Celestial risk factors in groin hernia repair and random statistical association: a nationwide register-based study
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Celestial phenomena like lunar phases and zodiac signs have been part of human culture since ancient times.[[1,2]] Many still believe that both zodiac signs and lunar phases influence daily life and to some extent even health.[[3,4]] However, these beliefs are often regarded as being superstitions without scientific evidence.[[5]] Nevertheless, zodiac signs and lunar phases are attributed significant meaning and value in daily life,[[5]] and many believe celestial factors carry significant attributes regarding health.[[6]] Additionally, there are ill-fated beliefs surrounding Friday the 13th, some say it is an “unlucky” day and some even believe it is an omen of death.[[7]]
The Danish Hernia Database provides data on almost all groin hernia repairs performed in Denmark with approximately 100% follow-up,[[8]] making it possible to assess the long-term effect of lunar phases, zodiac signs, and Friday the 13th on reoperation rate after groin hernia repair. There are many known patient-related and procedure-related risk factors for reoperation after groin hernia repair.[[9–11]] However, the impact of celestial-related risk factors have not previously been investigated.
We wished to investigate if it was possible to find an association between celestial phenomena and the reoperation rate after groin hernia repair. This study aimed to investigate how the 12 zodiac signs from Western astrology,[[12]] lunar phases, and Friday the 13th impacted the risk of reoperation after groin hernia repair.
Methods
We performed a register-based cohort study with nationwide prospectively collected data on groin hernia repairs which followed the REporting of studies Conducted using Observational Routinely collected health Data (RECORD) statement.[[13]] Data were obtained from the Danish Hernia Database[[8]] and the Danish Patient Safety Authority’s Online Register.[[14]] Data from the two databases were linked via surgeons’ unique authorisation IDs. The Danish Hernia Database contains data on patients’ sex, age, birthdate, (used to obtain patients’ zodiac sign), and date of operation (used to obtain the lunar phase at the time of operation). Furthermore, the Danish Hernia Database contains perioperative data such as side of the hernia, whether the repair was primary or recurrent, elective or emergency, type of hernia, and method of repair: Lichtenstein or laparoscopic TransAbdominal PrePeritoneal (TAPP) repair. The Danish Hernia Database also draws data from the Danish National Patient Registry[[15]] and the Danish Civil Registration System,[[16]] providing data on reoperation status, emigration, and deaths. The Danish Patient Safety Authority's Online Register contains data on all surgeons registered in Denmark such as surgeons’ authorisation ID,[[14]] which was included in the Danish Hernia Database from 2011, and the surgeons’ date of birth, making it possible to determine the surgeons’ zodiac sign.
Patients were included between January 2000 and December 2019. Recurrent groin hernia repair was defined as an operation for a new hernia on the same side as a previous repair. Since the same patient could be operated for a groin hernia on both sides, either at the same time or independently, we considered groins for inclusion rather than patients. This also ensured that a recurrent hernia was in fact on the same side as a previous hernia. Patients were followed until death, reoperation, or the end of the study period (1 January 2020).
Eligibility criteria for inclusion were primary groin hernia repairs performed in patients ≥18 years with either Lichtenstein or laparoscopic TAPP repair. TAPP technique accounts for >98% of laparoscopic repairs in Denmark,[[17]] therefore other laparoscopic approaches were not included. Both elective and emergency repairs were included. Groin hernias were considered primary if the repair was registered as a primary repair. Furthermore, we performed a “look back” for each groin from 1998 for previous repairs to identify recurrent hernias. Groin hernias were excluded if the first registered operation was a reoperation, the type of hernia was not registered, the repair was performed before 2000, or if patients had either emigrated or were living outside of Denmark. The inclusion criterion for surgeons was a valid authorisation ID entry. Surgeons were excluded if the authorisation ID was registered ≤2 times. The groin hernias were divided into two overlapping cohorts and analysed separately: one cohort with patients’ zodiac sign as the variable and one cohort with the surgeons’ zodiac sign as the variable.
The outcomes were risk of reoperation after groin hernia repair in relation to surgeons’ zodiac sign, patients’ zodiac sign, lunar phase at the time of repair, and whether the repair was performed on Friday the 13th vs other Fridays. The 12 zodiac signs used were from Western astrology based on the tropical zodiac.[[12]] The zodiac signs used in Western astrology originates from the ancient Babylonians who mapped the zodiac approximately 3,000 years ago.[[18]] Zodiac signs were assigned to the included surgeons and patients based on their birthdate.[[19]] In Western astrology, there are 12 signs: Capricorn, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio and Sagittarius. During a lunar cycle, the moon passes through four phases: the new, the waxing, the waning, and the full moon.[[20]] Data on lunar phases at the time of the repair (2000–2019) were obtained from the Copenhagen Planetarium’s Astronomy Department via personal contact. The day of the repair was assessed according to the Gregorian calendar which was used to identify Friday the 13th and other Fridays.
Subgroup analyses were performed to investigate the impact of lunar phases on the risk of reoperation for each surgeon zodiac sign. The reference for the subgroup analyses was the lunar phase with the lowest reoperation rate where all 12 surgeon zodiac signs were represented.
The statistical analyses were performed with SPSS (version 25.0, IBM, Armonk, NY, USA). Q-Q-plots and histograms were used to evaluate the distribution of data. Normally distributed, continuous data were presented as mean with standard deviation (SD), while non-normally distributed, continuous data were presented as median with interquartile range [IQR]. Categorical data were presented as crude reoperation rates and tested with the Chi-squared test. The difference in distribution of zodiac signs within groups was evaluated with 95% confidence intervals (CIs). Cox proportional hazard analyses was used to assess the risk of reoperation in relation to zodiac signs and lunar phases. The analyses were adjusted for patients’ sex, age, hernia type, and type of repair. Furthermore, the analyses for zodiac signs were adjusted for lunar phases while the analyses for lunar phases were adjusted for surgeons’ zodiac sign. The group with the lowest reoperation rate was used as reference. Risk of reoperation was presented as hazard ratios (HR) with 95% CIs. Findings were considered significant when p≤0.05.
Approval for this study was obtained from the Danish Data Protection Agency (P-2020-380). According to Danish law, approval from ethics committees and written informed consent were not required to conduct this study.
Results
In the surgeon zodiac sign cohort, we included 25,075 groin hernia repairs performed in 2011–2019. In the patient zodiac sign cohort, 151,901 groin hernia repairs were included between 2000–2019. The selection process of groin hernias in patients is shown in Figure 1.
View Figures & Tables.
The patient demographic and operative characteristics for the surgeon zodiac sign cohort and patient zodiac sign cohort are shown in Table 1.
The surgeon zodiac sign cohort included 541 surgeons, performing 25,075 repairs in 22,916 patients (see characteristics in Table 1). Of these repairs, 4%, 15%, and 5% were performed by surgeons born under the Capricorn, Aries and Scorpio, respectively, which differed significantly from the other surgeon zodiac signs. Among the 541 included surgeons, the 12 zodiac signs were evenly distributed (data not shown). The median follow-up [IQR] was 23 (12–33) months. The crude reoperation rates after groin hernia repair for each surgeon zodiac sign are shown in Figure 2.
The adjusted risk of reoperation after groin hernia repair based on surgeons’ zodiac sign is shown in Table 2. Surgeons born under the Sagittarius were used as reference since they had the lowest crude reoperation rate (1.5%). The adjusted analyses showed significantly higher risk of reoperation when the performing surgeon was born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo compared with the Sagittarius, see Table 2.
We performed subgroup analyses, investigating how lunar phases at the time of repair affected the risk of reoperation for each of the 12 surgeon zodiac signs. The waning moon was used as reference since it was the phase with the lowest reoperation rate, where all 12 surgeon zodiac signs were represented. The subgroup analyses (see Table 3) showed increased risk of reoperation after repairs performed by surgeons born under the Capricorn (HR 5.39) and Aquarius (HR 4.81) during the new compared with the waning moon. In addition, surgeons born under the Capricorn had an increased risk of reoperation (HR 9.13) during the full compared with the waning moon. Lastly, we found an increased risk of reoperation after repairs performed by surgeons born under the Pisces (HR 1.99) and Libra (HR 2.24) during the waxing compared with the waning moon.
Crude reoperation rate based on lunar phases seemed higher during the new (2.9%) and the waxing moon (2.5%) than during the waning (2.1%) and the full moon (2.0%). Table 4 shows the risk of reoperation after groin hernia repair in relation to the lunar phase on the day of the repair in the surgeon zodiac sign cohort. There was a significantly higher risk of reoperation after repairs performed during the new and the waxing moon compared with the waning moon.
The patient zodiac sign cohort included 151,901 groins hernia repairs, performed in 142,872 patients (see characteristics in Table 1). The median follow-up [IQR] was 93 [43–156] months. The crude reoperation rates were similar for all 12 patient zodiac signs (Appendix 1). Furthermore, there were no differences in the HRs amongst the different patient zodiac signs. The Cox regression was adjusted for patients’ sex, age, type of hernia, type of repair, and lunar phase (analyses not shown).
There were 20,406 repairs performed on regular Fridays and 675 repairs on a Friday that fell on the 13th of the month. The crude reoperation rate after repairs performed on Friday the 13th was 4.5% and 4.3% on regular Fridays (p͏=0.826).
Discussion
We found a significantly higher risk of reoperation after groin hernia repair performed by surgeons born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo compared with the Sagittarius. Repairs performed under the new or the waxing moon were associated with higher risk of reoperation compared with repairs performed under the waning moon, whereas patients’ zodiac sign or Friday the 13th did not affect the risk of reoperation.
Surgeon zodiac sign was a significant risk factor for reoperation after groin hernia repair, and we investigated whether the lunar phases could reduce the effect of the surgeons’ zodiac sign. This indicated that there was a significantly increased risk of reoperation during the full moon for surgeons born under the Capricorn and Aquarius. Furthermore, repairs performed by surgeons born under the Capricorn were associated with an increased risk of reoperation during the new moon. Surgeons born under the Pisces or Libra had higher risk of reoperation during the waxing moon. In the surgeon zodiac sign cohort, repairs performed during the waxing or the full moon were associated with a higher risk of reoperation compared with the waning moon. It could therefore be argued that surgeons could consider lunar phases when scheduling groin hernia repairs to minimise the risk of reoperation associated with the waxing moon. However, the moon is in the waxing phase approximately two weeks during every cycle of 29.5 days[[20]] and, thus difficult to avoid.
This study is an example of how statistical analyses can yield significant findings and the interpretation of such findings are key when distinguishing between random association and actual causality. We presented various analyses indicating that surgeons’ zodiac sign and lunar phases impacted the risk of reoperation after groin hernia repair. According to our data and analyses, one possible conclusion could be that surgeons born under the Sagittarius were better hernia surgeons than surgeons born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo. However, such a conclusion cannot be drawn without careful consideration: is it plausible that there is a cause-and-effect relation between the risk of reoperation after groin hernia repair and factors such as surgeons’ zodiac sign and lunar phase? To answer this question, we considered the aspect of causality. When assessing causality Bradford Hill’s nine criteria for causality are considered the golden standard.[[21]] Particularly, we will highlight the specificity, the plausibility, and the coherence of the evidence presented in this study. The specificity of our findings is difficult to quantify, but since there are many risk factors associated with the risk of reoperation after inguinal hernia repair,[[9–11]] it is likely that other factors could have affected the risk of reoperation, and thus the specificity of our findings is likely not high. Most health personnel would deem it biologically implausible that zodiac sign and lunar phase could affect the outcome of surgical interventions since zodiac sign and lunar phase are considered popular superstitions without supporting evidence. Furthermore, there are no biological pathways where factors such as zodiac sign or lunar phases are known to affect the outcome, and this assumption would seem contradictory to the bases of modern Western medicine. To our knowledge, only one previous study has investigated the impact of lunar phases and the short-term outcome after inguinal hernia repair and found that the lunar phase did not affect the risk of post-operative pain.[[22]] Other previous studies have investigated the impact of zodiac sign at the time of operation and the lunar phases on intraoperative blood loss,[[23]] various outcomes in radical cystectomy,[[24]] intracranial aneurysm rupture,[[25]] and elective spine surgery.[[26]] However, these results cannot be compared with our findings regarding groin hernia repair. Thus, there is no coherent evidence in the literature supporting the findings of the present study, and the findings presented here should be interpretated with caution before making conclusions regarding causality between zodiac sign, lunar phases and the risk of reoperation after groin hernia repair. Our findings should be interpreted as random associations rather than a cause-and-effect relationship, underlining that researchers, editors, peer reviewers, and readers should interpretate data analyses and statistical associations with caution. A conclusion regarding a cause-and-effect relation between celestial risk factors and groin hernia repair cannot be made solely based on the evidence presented in this study. That would require further studies, adding evidence to the cause-and-effect relationship.
This study has several methodological strengths. The Danish Hernia Database[[8]] and the Danish Patient Safety Authority's Online Register[[14]] both have nationwide coverage. Furthermore, the Danish Hernia Database draws data from the National Patient Registry,[[15]] ensuring a follow-up close to 100% in the Danish Hernia Database.[[8]] Data on lunar phases were obtained from the Copenhagen Planetarium’s Astronomy Department, ensuring high accuracy of the dates and times of the lunar phases. However, there are also limitations to this study. Data on the hernia defect size were not available in the majority (70%) of the included groins hernias and were therefore not reported. It is important to highlight the statistical analyses of the present study. We conducted several analyses with multiple variables. In theory, one in 20 analyses will coincidently result in a significant finding with a significance level of 0.05. This study included a large, representative sample size and we do not suspect a type II error in the patient zodiac sign cohort, where we did not find any significant effect of patients’ zodiac sign on the risk of reoperation. In the surgeon zodiac sign cohort, we found a significant effect of both surgeon zodiac sign and lunar phase on the risk of reoperation. It is possible that this significant finding was in fact a statistical type I error, thus falsely rejecting the null hypothesis. Furthermore, we conducted 62 Cox regressions (11 for patient zodiac sign, 11 for surgeon zodiac sign, 36 for the subgroup analyses for lunar phases in the surgeon zodiac sign cohort, and 3 for lunar phases alone), and we did not adjust for multiple testing, which again increased the risk of a type I error. Thus, the findings in this study may have statistical significance; however, the clinical significance is debatable, and the evidence presented in this study can be regarded as a random association as a result of statistical analyses with large sample sizes, and not necessarily a causal relation.
In conclusion, surgeons’ zodiac sign significantly affected the risk of reoperation after groin hernia repair, and surgeons born under the Sagittarius had a significantly lower risk of reoperation after groin hernia repair. The new and the waxing moon were associated with a significantly increased risk of reoperation. Patients’ zodiac sign or Friday the 13th did not affect the risk of reoperation. This study showed that it is relatively easy to find random associations in research with very large sample sizes, and it is important that findings, although statistically significant, should be considered with caution before concluding that there is a cause-and-effect relation.
View Appendix 1.
Summary
Abstract
Aim
We aimed to investigate how celestial phenomena like zodiac signs, lunar phases, and Friday the 13th impacted the risk of reoperation after groin hernia repair.
Method
We conducted a nationwide register-based study based on the Danish Hernia Database and Danish Patient Safety Authority’s Online Register between 2000–2019. We included patients ≥18 years undergoing open Lichtenstein or laparoscopic groin hernia repair. The main outcomes were risk of reoperation after groin hernia repair in relation to patient and surgeon zodiac sign, lunar phase at the time of the repair, and Friday the 13th vs other Fridays.
Results
151,901 groin hernias were included in the analysis of patient zodiac sign, and 25,075 groin hernias were included in the analysis of surgeon zodiac sign. Compared with the Sagittarius, there was a significantly higher risk of reoperation (HR [95% CI]) if the performing surgeon was born under the Capricorn (1.93 [1.16–3.12]); Pisces (1.68 [1.09–2.57]); Aries (1.61 [1.07–2.38]); Taurus (1.62 [1.04–2.54]); Cancer (2.21 [1.48–3.28]); or Virgo (1.71 [1.13–2.59]). Repairs performed under the waxing (1.23 [1.03–1.46]) and the new moon (1.54 [1.11–2.13]) had significantly higher risk of reoperation (HR [95% CI]) compared with the waning moon. Neither patient zodiac sign nor Friday the 13th affected risk of reoperation after groin hernia repair.
Conclusion
Surgeons’ zodiac sign and lunar phase significantly affected the risk of reoperation after groin hernia repair. Neither patients’ zodiac sign nor Friday the 13th influenced on the risk of reoperation after groin hernia repair. This indicates why significant findings should be considered carefully to distinguish between random statistical association and cause-and-effect relations.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
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Celestial risk factors in groin hernia repair and random statistical association: a nationwide register-based study
View Article PDF
Celestial phenomena like lunar phases and zodiac signs have been part of human culture since ancient times.[[1,2]] Many still believe that both zodiac signs and lunar phases influence daily life and to some extent even health.[[3,4]] However, these beliefs are often regarded as being superstitions without scientific evidence.[[5]] Nevertheless, zodiac signs and lunar phases are attributed significant meaning and value in daily life,[[5]] and many believe celestial factors carry significant attributes regarding health.[[6]] Additionally, there are ill-fated beliefs surrounding Friday the 13th, some say it is an “unlucky” day and some even believe it is an omen of death.[[7]]
The Danish Hernia Database provides data on almost all groin hernia repairs performed in Denmark with approximately 100% follow-up,[[8]] making it possible to assess the long-term effect of lunar phases, zodiac signs, and Friday the 13th on reoperation rate after groin hernia repair. There are many known patient-related and procedure-related risk factors for reoperation after groin hernia repair.[[9–11]] However, the impact of celestial-related risk factors have not previously been investigated.
We wished to investigate if it was possible to find an association between celestial phenomena and the reoperation rate after groin hernia repair. This study aimed to investigate how the 12 zodiac signs from Western astrology,[[12]] lunar phases, and Friday the 13th impacted the risk of reoperation after groin hernia repair.
Methods
We performed a register-based cohort study with nationwide prospectively collected data on groin hernia repairs which followed the REporting of studies Conducted using Observational Routinely collected health Data (RECORD) statement.[[13]] Data were obtained from the Danish Hernia Database[[8]] and the Danish Patient Safety Authority’s Online Register.[[14]] Data from the two databases were linked via surgeons’ unique authorisation IDs. The Danish Hernia Database contains data on patients’ sex, age, birthdate, (used to obtain patients’ zodiac sign), and date of operation (used to obtain the lunar phase at the time of operation). Furthermore, the Danish Hernia Database contains perioperative data such as side of the hernia, whether the repair was primary or recurrent, elective or emergency, type of hernia, and method of repair: Lichtenstein or laparoscopic TransAbdominal PrePeritoneal (TAPP) repair. The Danish Hernia Database also draws data from the Danish National Patient Registry[[15]] and the Danish Civil Registration System,[[16]] providing data on reoperation status, emigration, and deaths. The Danish Patient Safety Authority's Online Register contains data on all surgeons registered in Denmark such as surgeons’ authorisation ID,[[14]] which was included in the Danish Hernia Database from 2011, and the surgeons’ date of birth, making it possible to determine the surgeons’ zodiac sign.
Patients were included between January 2000 and December 2019. Recurrent groin hernia repair was defined as an operation for a new hernia on the same side as a previous repair. Since the same patient could be operated for a groin hernia on both sides, either at the same time or independently, we considered groins for inclusion rather than patients. This also ensured that a recurrent hernia was in fact on the same side as a previous hernia. Patients were followed until death, reoperation, or the end of the study period (1 January 2020).
Eligibility criteria for inclusion were primary groin hernia repairs performed in patients ≥18 years with either Lichtenstein or laparoscopic TAPP repair. TAPP technique accounts for >98% of laparoscopic repairs in Denmark,[[17]] therefore other laparoscopic approaches were not included. Both elective and emergency repairs were included. Groin hernias were considered primary if the repair was registered as a primary repair. Furthermore, we performed a “look back” for each groin from 1998 for previous repairs to identify recurrent hernias. Groin hernias were excluded if the first registered operation was a reoperation, the type of hernia was not registered, the repair was performed before 2000, or if patients had either emigrated or were living outside of Denmark. The inclusion criterion for surgeons was a valid authorisation ID entry. Surgeons were excluded if the authorisation ID was registered ≤2 times. The groin hernias were divided into two overlapping cohorts and analysed separately: one cohort with patients’ zodiac sign as the variable and one cohort with the surgeons’ zodiac sign as the variable.
The outcomes were risk of reoperation after groin hernia repair in relation to surgeons’ zodiac sign, patients’ zodiac sign, lunar phase at the time of repair, and whether the repair was performed on Friday the 13th vs other Fridays. The 12 zodiac signs used were from Western astrology based on the tropical zodiac.[[12]] The zodiac signs used in Western astrology originates from the ancient Babylonians who mapped the zodiac approximately 3,000 years ago.[[18]] Zodiac signs were assigned to the included surgeons and patients based on their birthdate.[[19]] In Western astrology, there are 12 signs: Capricorn, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio and Sagittarius. During a lunar cycle, the moon passes through four phases: the new, the waxing, the waning, and the full moon.[[20]] Data on lunar phases at the time of the repair (2000–2019) were obtained from the Copenhagen Planetarium’s Astronomy Department via personal contact. The day of the repair was assessed according to the Gregorian calendar which was used to identify Friday the 13th and other Fridays.
Subgroup analyses were performed to investigate the impact of lunar phases on the risk of reoperation for each surgeon zodiac sign. The reference for the subgroup analyses was the lunar phase with the lowest reoperation rate where all 12 surgeon zodiac signs were represented.
The statistical analyses were performed with SPSS (version 25.0, IBM, Armonk, NY, USA). Q-Q-plots and histograms were used to evaluate the distribution of data. Normally distributed, continuous data were presented as mean with standard deviation (SD), while non-normally distributed, continuous data were presented as median with interquartile range [IQR]. Categorical data were presented as crude reoperation rates and tested with the Chi-squared test. The difference in distribution of zodiac signs within groups was evaluated with 95% confidence intervals (CIs). Cox proportional hazard analyses was used to assess the risk of reoperation in relation to zodiac signs and lunar phases. The analyses were adjusted for patients’ sex, age, hernia type, and type of repair. Furthermore, the analyses for zodiac signs were adjusted for lunar phases while the analyses for lunar phases were adjusted for surgeons’ zodiac sign. The group with the lowest reoperation rate was used as reference. Risk of reoperation was presented as hazard ratios (HR) with 95% CIs. Findings were considered significant when p≤0.05.
Approval for this study was obtained from the Danish Data Protection Agency (P-2020-380). According to Danish law, approval from ethics committees and written informed consent were not required to conduct this study.
Results
In the surgeon zodiac sign cohort, we included 25,075 groin hernia repairs performed in 2011–2019. In the patient zodiac sign cohort, 151,901 groin hernia repairs were included between 2000–2019. The selection process of groin hernias in patients is shown in Figure 1.
View Figures & Tables.
The patient demographic and operative characteristics for the surgeon zodiac sign cohort and patient zodiac sign cohort are shown in Table 1.
The surgeon zodiac sign cohort included 541 surgeons, performing 25,075 repairs in 22,916 patients (see characteristics in Table 1). Of these repairs, 4%, 15%, and 5% were performed by surgeons born under the Capricorn, Aries and Scorpio, respectively, which differed significantly from the other surgeon zodiac signs. Among the 541 included surgeons, the 12 zodiac signs were evenly distributed (data not shown). The median follow-up [IQR] was 23 (12–33) months. The crude reoperation rates after groin hernia repair for each surgeon zodiac sign are shown in Figure 2.
The adjusted risk of reoperation after groin hernia repair based on surgeons’ zodiac sign is shown in Table 2. Surgeons born under the Sagittarius were used as reference since they had the lowest crude reoperation rate (1.5%). The adjusted analyses showed significantly higher risk of reoperation when the performing surgeon was born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo compared with the Sagittarius, see Table 2.
We performed subgroup analyses, investigating how lunar phases at the time of repair affected the risk of reoperation for each of the 12 surgeon zodiac signs. The waning moon was used as reference since it was the phase with the lowest reoperation rate, where all 12 surgeon zodiac signs were represented. The subgroup analyses (see Table 3) showed increased risk of reoperation after repairs performed by surgeons born under the Capricorn (HR 5.39) and Aquarius (HR 4.81) during the new compared with the waning moon. In addition, surgeons born under the Capricorn had an increased risk of reoperation (HR 9.13) during the full compared with the waning moon. Lastly, we found an increased risk of reoperation after repairs performed by surgeons born under the Pisces (HR 1.99) and Libra (HR 2.24) during the waxing compared with the waning moon.
Crude reoperation rate based on lunar phases seemed higher during the new (2.9%) and the waxing moon (2.5%) than during the waning (2.1%) and the full moon (2.0%). Table 4 shows the risk of reoperation after groin hernia repair in relation to the lunar phase on the day of the repair in the surgeon zodiac sign cohort. There was a significantly higher risk of reoperation after repairs performed during the new and the waxing moon compared with the waning moon.
The patient zodiac sign cohort included 151,901 groins hernia repairs, performed in 142,872 patients (see characteristics in Table 1). The median follow-up [IQR] was 93 [43–156] months. The crude reoperation rates were similar for all 12 patient zodiac signs (Appendix 1). Furthermore, there were no differences in the HRs amongst the different patient zodiac signs. The Cox regression was adjusted for patients’ sex, age, type of hernia, type of repair, and lunar phase (analyses not shown).
There were 20,406 repairs performed on regular Fridays and 675 repairs on a Friday that fell on the 13th of the month. The crude reoperation rate after repairs performed on Friday the 13th was 4.5% and 4.3% on regular Fridays (p͏=0.826).
Discussion
We found a significantly higher risk of reoperation after groin hernia repair performed by surgeons born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo compared with the Sagittarius. Repairs performed under the new or the waxing moon were associated with higher risk of reoperation compared with repairs performed under the waning moon, whereas patients’ zodiac sign or Friday the 13th did not affect the risk of reoperation.
Surgeon zodiac sign was a significant risk factor for reoperation after groin hernia repair, and we investigated whether the lunar phases could reduce the effect of the surgeons’ zodiac sign. This indicated that there was a significantly increased risk of reoperation during the full moon for surgeons born under the Capricorn and Aquarius. Furthermore, repairs performed by surgeons born under the Capricorn were associated with an increased risk of reoperation during the new moon. Surgeons born under the Pisces or Libra had higher risk of reoperation during the waxing moon. In the surgeon zodiac sign cohort, repairs performed during the waxing or the full moon were associated with a higher risk of reoperation compared with the waning moon. It could therefore be argued that surgeons could consider lunar phases when scheduling groin hernia repairs to minimise the risk of reoperation associated with the waxing moon. However, the moon is in the waxing phase approximately two weeks during every cycle of 29.5 days[[20]] and, thus difficult to avoid.
This study is an example of how statistical analyses can yield significant findings and the interpretation of such findings are key when distinguishing between random association and actual causality. We presented various analyses indicating that surgeons’ zodiac sign and lunar phases impacted the risk of reoperation after groin hernia repair. According to our data and analyses, one possible conclusion could be that surgeons born under the Sagittarius were better hernia surgeons than surgeons born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo. However, such a conclusion cannot be drawn without careful consideration: is it plausible that there is a cause-and-effect relation between the risk of reoperation after groin hernia repair and factors such as surgeons’ zodiac sign and lunar phase? To answer this question, we considered the aspect of causality. When assessing causality Bradford Hill’s nine criteria for causality are considered the golden standard.[[21]] Particularly, we will highlight the specificity, the plausibility, and the coherence of the evidence presented in this study. The specificity of our findings is difficult to quantify, but since there are many risk factors associated with the risk of reoperation after inguinal hernia repair,[[9–11]] it is likely that other factors could have affected the risk of reoperation, and thus the specificity of our findings is likely not high. Most health personnel would deem it biologically implausible that zodiac sign and lunar phase could affect the outcome of surgical interventions since zodiac sign and lunar phase are considered popular superstitions without supporting evidence. Furthermore, there are no biological pathways where factors such as zodiac sign or lunar phases are known to affect the outcome, and this assumption would seem contradictory to the bases of modern Western medicine. To our knowledge, only one previous study has investigated the impact of lunar phases and the short-term outcome after inguinal hernia repair and found that the lunar phase did not affect the risk of post-operative pain.[[22]] Other previous studies have investigated the impact of zodiac sign at the time of operation and the lunar phases on intraoperative blood loss,[[23]] various outcomes in radical cystectomy,[[24]] intracranial aneurysm rupture,[[25]] and elective spine surgery.[[26]] However, these results cannot be compared with our findings regarding groin hernia repair. Thus, there is no coherent evidence in the literature supporting the findings of the present study, and the findings presented here should be interpretated with caution before making conclusions regarding causality between zodiac sign, lunar phases and the risk of reoperation after groin hernia repair. Our findings should be interpreted as random associations rather than a cause-and-effect relationship, underlining that researchers, editors, peer reviewers, and readers should interpretate data analyses and statistical associations with caution. A conclusion regarding a cause-and-effect relation between celestial risk factors and groin hernia repair cannot be made solely based on the evidence presented in this study. That would require further studies, adding evidence to the cause-and-effect relationship.
This study has several methodological strengths. The Danish Hernia Database[[8]] and the Danish Patient Safety Authority's Online Register[[14]] both have nationwide coverage. Furthermore, the Danish Hernia Database draws data from the National Patient Registry,[[15]] ensuring a follow-up close to 100% in the Danish Hernia Database.[[8]] Data on lunar phases were obtained from the Copenhagen Planetarium’s Astronomy Department, ensuring high accuracy of the dates and times of the lunar phases. However, there are also limitations to this study. Data on the hernia defect size were not available in the majority (70%) of the included groins hernias and were therefore not reported. It is important to highlight the statistical analyses of the present study. We conducted several analyses with multiple variables. In theory, one in 20 analyses will coincidently result in a significant finding with a significance level of 0.05. This study included a large, representative sample size and we do not suspect a type II error in the patient zodiac sign cohort, where we did not find any significant effect of patients’ zodiac sign on the risk of reoperation. In the surgeon zodiac sign cohort, we found a significant effect of both surgeon zodiac sign and lunar phase on the risk of reoperation. It is possible that this significant finding was in fact a statistical type I error, thus falsely rejecting the null hypothesis. Furthermore, we conducted 62 Cox regressions (11 for patient zodiac sign, 11 for surgeon zodiac sign, 36 for the subgroup analyses for lunar phases in the surgeon zodiac sign cohort, and 3 for lunar phases alone), and we did not adjust for multiple testing, which again increased the risk of a type I error. Thus, the findings in this study may have statistical significance; however, the clinical significance is debatable, and the evidence presented in this study can be regarded as a random association as a result of statistical analyses with large sample sizes, and not necessarily a causal relation.
In conclusion, surgeons’ zodiac sign significantly affected the risk of reoperation after groin hernia repair, and surgeons born under the Sagittarius had a significantly lower risk of reoperation after groin hernia repair. The new and the waxing moon were associated with a significantly increased risk of reoperation. Patients’ zodiac sign or Friday the 13th did not affect the risk of reoperation. This study showed that it is relatively easy to find random associations in research with very large sample sizes, and it is important that findings, although statistically significant, should be considered with caution before concluding that there is a cause-and-effect relation.
View Appendix 1.
Summary
Abstract
Aim
We aimed to investigate how celestial phenomena like zodiac signs, lunar phases, and Friday the 13th impacted the risk of reoperation after groin hernia repair.
Method
We conducted a nationwide register-based study based on the Danish Hernia Database and Danish Patient Safety Authority’s Online Register between 2000–2019. We included patients ≥18 years undergoing open Lichtenstein or laparoscopic groin hernia repair. The main outcomes were risk of reoperation after groin hernia repair in relation to patient and surgeon zodiac sign, lunar phase at the time of the repair, and Friday the 13th vs other Fridays.
Results
151,901 groin hernias were included in the analysis of patient zodiac sign, and 25,075 groin hernias were included in the analysis of surgeon zodiac sign. Compared with the Sagittarius, there was a significantly higher risk of reoperation (HR [95% CI]) if the performing surgeon was born under the Capricorn (1.93 [1.16–3.12]); Pisces (1.68 [1.09–2.57]); Aries (1.61 [1.07–2.38]); Taurus (1.62 [1.04–2.54]); Cancer (2.21 [1.48–3.28]); or Virgo (1.71 [1.13–2.59]). Repairs performed under the waxing (1.23 [1.03–1.46]) and the new moon (1.54 [1.11–2.13]) had significantly higher risk of reoperation (HR [95% CI]) compared with the waning moon. Neither patient zodiac sign nor Friday the 13th affected risk of reoperation after groin hernia repair.
Conclusion
Surgeons’ zodiac sign and lunar phase significantly affected the risk of reoperation after groin hernia repair. Neither patients’ zodiac sign nor Friday the 13th influenced on the risk of reoperation after groin hernia repair. This indicates why significant findings should be considered carefully to distinguish between random statistical association and cause-and-effect relations.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
1) Webster D. The origin of the signs of the zodiac: an interpretation from the psychological viewpoint. American Imago. 1940; 1:31-47.
2) Montgomery SL. How the moon began: ideas of lunar reality in antiquity. In: The moon & the Western imagination. Tucson. University of Arizona Press; 1999. pp11-29.
3) Chakraborty U. Effects of different phases of the lunar month on humans. Biol Rhythm Res. 2014; 45:383-396.
4) Besley J, Hill D. Science and technology: public attitudes, knowledge, and interest [Internet]. Alexandria, Virginia, USA: National Center for Science and Engineering Statistics; May 2020 [cited 2022 Feb 9]. Available from: https://ncses.nsf.gov/pubs/nsb20207/public-familiarity-with-s-t-facts#pseudoscience.
5) Zarka P. Astronomy and astrology. Proc Int Astron Union. 2009;5:420-425.
6) Vyse SA. Believing in magic. In: Believing in magic: the psycology of superstition. New York. Oxford University Press; 2014. pp3-29.
7) Scanlon TJ, Luben RN, Scanlon FL, Singleton N. Is Friday the 13th bad for your health? BMJ. 1993; 307:1584-1586.
8) Friis-Andersen H, Bisgaard T. The Danish inguinal hernia database. Clin Epidemiol. 2016; 8:521-524.
9) Burcharth J, Pommergaard H-C, Bisgaard T, Rosenberg J. Patient-related risk factors for recurrence after inguinal hernia repair: a systematic review and meta-analysis of observational studies. Surg Innov. 2015; 22:303-317.
10) Schmedt CG, Sauerland S, Bittner R. Comparison of endoscopic procedures vs Lichtenstein and other open mesh techniques for inguinal hernia repair: a meta-analysis of randomized controlled trials. Surg Endosc. 2005; 19:188-199.
11) Zhong C, Wu B, Yang Z, et al. A meta-analysis comparing lightweight meshes with heavyweight meshes in Lichtenstein inguinal hernia repair. Surg Innov. 2013; 20:24-31.
12) Lewis JR. The astrology book: the encyclopedia of heavenly influences. Canton. Visible Ink Press; 2003.
13) Benchimol EI, Smeeth L, Guttmann A, et al. The REporting of studies Conducted using Observational Routinely-collected health Data (RECORD) Statement. PLoS Med. 2015; 12:e1001885.
14) Information about the Online register [Internet]. Denmark: Danish Patient Safety Authority. [cited 2022 Feb 9]. Available from: https://en.stps.dk/en/health-professionals-and-authorities/online-register-registered-health-professionals/information-about-the-online-register/.
15) Schmidt M, Schmidt SAJ, Sandegaard JL, Ehrenstein V, Pedersen L, Sørensen TH. The Danish National Patient Registry: a review of content, data quality, and research potential. Clin Epidemiol. 2015; 7:449-490.
16) Pedersen CB. The Danish Civil Registration System. Scand J Public Health. 2011; 39:22-25.
17) Andresen K, Friis-Andersen H, Rosenberg J. Laparoscopic repair of primary inguinal hernia performed in public hospitals or low-volume centers have increased risk of reoperation for recurrence. Surg Innov. 2016; 23:142-147.
18) Constellations and the Calendar [Internet]. NASA; Sep 2016 [cited 2022 Feb 9]. Available from: https://nasa.tumblr.com/post/150688852794/zodiac.
19) Horoscopes [Internet]. Ireland: Old Moore’s Almanac; 2019 [cited 2022 Feb 9]. Available from: https://oldmooresalmanac.com/horoscopes/.
20) Solar system exploration, Earth’s moon. Lunar phases and eclipses [Internet]. USA: NASA [cited 2022 Feb 9]. Available from: https://solarsystem.nasa.gov/moons/earths-moon/lunar-phases-and-eclipses/.
21) Bradford Hill A. The environment and disease: association or causation? Proc R Soc Med. 1965; 58:296-300.
22) Holzheimer R, Nitz C, Gresser U. Lunar phase does not influence surgical quality. Eur J Med Res. 2003; 8:414-418.
23) Schuld J, Slotta JE, Schuld S, Kollmar O, Schilling MK, Richter S. Popular belief meets surgical reality: impact of lunar phases, Friday the 13th and zodiac signs on emergency operations and intraoperative blood loss. World J Surg. 201; 35:1945-1949.
24) May M, Braun KP, Helke C, et al. Lunar phases and zodiac signs do not influence quality of radical cystectomy-a statistical analysis of 452 patients with invasive bladder cancer. Int Urol Nephrol. 2007; 39:1023-1030.
25) Bunevicius A, Gendvilaite A, Deltuva VP, Tamasauskas A. The association between lunar phase and intracranial aneurysm rupture: myth or reality? Own data and systematic review. BMC Neurol. 2017; 17:99.
26) Joswig H, Stienen MN, Hock C, Hildebrandt G, Surbeck W. The influence of lunar phases and zodiac sign ‘Leo’ on perioperative complications and outcome in elective spine surgery. Acta Neurochir. 2016; 158:1095-1101.
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Celestial risk factors in groin hernia repair and random statistical association: a nationwide register-based study
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Celestial phenomena like lunar phases and zodiac signs have been part of human culture since ancient times.[[1,2]] Many still believe that both zodiac signs and lunar phases influence daily life and to some extent even health.[[3,4]] However, these beliefs are often regarded as being superstitions without scientific evidence.[[5]] Nevertheless, zodiac signs and lunar phases are attributed significant meaning and value in daily life,[[5]] and many believe celestial factors carry significant attributes regarding health.[[6]] Additionally, there are ill-fated beliefs surrounding Friday the 13th, some say it is an “unlucky” day and some even believe it is an omen of death.[[7]]
The Danish Hernia Database provides data on almost all groin hernia repairs performed in Denmark with approximately 100% follow-up,[[8]] making it possible to assess the long-term effect of lunar phases, zodiac signs, and Friday the 13th on reoperation rate after groin hernia repair. There are many known patient-related and procedure-related risk factors for reoperation after groin hernia repair.[[9–11]] However, the impact of celestial-related risk factors have not previously been investigated.
We wished to investigate if it was possible to find an association between celestial phenomena and the reoperation rate after groin hernia repair. This study aimed to investigate how the 12 zodiac signs from Western astrology,[[12]] lunar phases, and Friday the 13th impacted the risk of reoperation after groin hernia repair.
Methods
We performed a register-based cohort study with nationwide prospectively collected data on groin hernia repairs which followed the REporting of studies Conducted using Observational Routinely collected health Data (RECORD) statement.[[13]] Data were obtained from the Danish Hernia Database[[8]] and the Danish Patient Safety Authority’s Online Register.[[14]] Data from the two databases were linked via surgeons’ unique authorisation IDs. The Danish Hernia Database contains data on patients’ sex, age, birthdate, (used to obtain patients’ zodiac sign), and date of operation (used to obtain the lunar phase at the time of operation). Furthermore, the Danish Hernia Database contains perioperative data such as side of the hernia, whether the repair was primary or recurrent, elective or emergency, type of hernia, and method of repair: Lichtenstein or laparoscopic TransAbdominal PrePeritoneal (TAPP) repair. The Danish Hernia Database also draws data from the Danish National Patient Registry[[15]] and the Danish Civil Registration System,[[16]] providing data on reoperation status, emigration, and deaths. The Danish Patient Safety Authority's Online Register contains data on all surgeons registered in Denmark such as surgeons’ authorisation ID,[[14]] which was included in the Danish Hernia Database from 2011, and the surgeons’ date of birth, making it possible to determine the surgeons’ zodiac sign.
Patients were included between January 2000 and December 2019. Recurrent groin hernia repair was defined as an operation for a new hernia on the same side as a previous repair. Since the same patient could be operated for a groin hernia on both sides, either at the same time or independently, we considered groins for inclusion rather than patients. This also ensured that a recurrent hernia was in fact on the same side as a previous hernia. Patients were followed until death, reoperation, or the end of the study period (1 January 2020).
Eligibility criteria for inclusion were primary groin hernia repairs performed in patients ≥18 years with either Lichtenstein or laparoscopic TAPP repair. TAPP technique accounts for >98% of laparoscopic repairs in Denmark,[[17]] therefore other laparoscopic approaches were not included. Both elective and emergency repairs were included. Groin hernias were considered primary if the repair was registered as a primary repair. Furthermore, we performed a “look back” for each groin from 1998 for previous repairs to identify recurrent hernias. Groin hernias were excluded if the first registered operation was a reoperation, the type of hernia was not registered, the repair was performed before 2000, or if patients had either emigrated or were living outside of Denmark. The inclusion criterion for surgeons was a valid authorisation ID entry. Surgeons were excluded if the authorisation ID was registered ≤2 times. The groin hernias were divided into two overlapping cohorts and analysed separately: one cohort with patients’ zodiac sign as the variable and one cohort with the surgeons’ zodiac sign as the variable.
The outcomes were risk of reoperation after groin hernia repair in relation to surgeons’ zodiac sign, patients’ zodiac sign, lunar phase at the time of repair, and whether the repair was performed on Friday the 13th vs other Fridays. The 12 zodiac signs used were from Western astrology based on the tropical zodiac.[[12]] The zodiac signs used in Western astrology originates from the ancient Babylonians who mapped the zodiac approximately 3,000 years ago.[[18]] Zodiac signs were assigned to the included surgeons and patients based on their birthdate.[[19]] In Western astrology, there are 12 signs: Capricorn, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio and Sagittarius. During a lunar cycle, the moon passes through four phases: the new, the waxing, the waning, and the full moon.[[20]] Data on lunar phases at the time of the repair (2000–2019) were obtained from the Copenhagen Planetarium’s Astronomy Department via personal contact. The day of the repair was assessed according to the Gregorian calendar which was used to identify Friday the 13th and other Fridays.
Subgroup analyses were performed to investigate the impact of lunar phases on the risk of reoperation for each surgeon zodiac sign. The reference for the subgroup analyses was the lunar phase with the lowest reoperation rate where all 12 surgeon zodiac signs were represented.
The statistical analyses were performed with SPSS (version 25.0, IBM, Armonk, NY, USA). Q-Q-plots and histograms were used to evaluate the distribution of data. Normally distributed, continuous data were presented as mean with standard deviation (SD), while non-normally distributed, continuous data were presented as median with interquartile range [IQR]. Categorical data were presented as crude reoperation rates and tested with the Chi-squared test. The difference in distribution of zodiac signs within groups was evaluated with 95% confidence intervals (CIs). Cox proportional hazard analyses was used to assess the risk of reoperation in relation to zodiac signs and lunar phases. The analyses were adjusted for patients’ sex, age, hernia type, and type of repair. Furthermore, the analyses for zodiac signs were adjusted for lunar phases while the analyses for lunar phases were adjusted for surgeons’ zodiac sign. The group with the lowest reoperation rate was used as reference. Risk of reoperation was presented as hazard ratios (HR) with 95% CIs. Findings were considered significant when p≤0.05.
Approval for this study was obtained from the Danish Data Protection Agency (P-2020-380). According to Danish law, approval from ethics committees and written informed consent were not required to conduct this study.
Results
In the surgeon zodiac sign cohort, we included 25,075 groin hernia repairs performed in 2011–2019. In the patient zodiac sign cohort, 151,901 groin hernia repairs were included between 2000–2019. The selection process of groin hernias in patients is shown in Figure 1.
View Figures & Tables.
The patient demographic and operative characteristics for the surgeon zodiac sign cohort and patient zodiac sign cohort are shown in Table 1.
The surgeon zodiac sign cohort included 541 surgeons, performing 25,075 repairs in 22,916 patients (see characteristics in Table 1). Of these repairs, 4%, 15%, and 5% were performed by surgeons born under the Capricorn, Aries and Scorpio, respectively, which differed significantly from the other surgeon zodiac signs. Among the 541 included surgeons, the 12 zodiac signs were evenly distributed (data not shown). The median follow-up [IQR] was 23 (12–33) months. The crude reoperation rates after groin hernia repair for each surgeon zodiac sign are shown in Figure 2.
The adjusted risk of reoperation after groin hernia repair based on surgeons’ zodiac sign is shown in Table 2. Surgeons born under the Sagittarius were used as reference since they had the lowest crude reoperation rate (1.5%). The adjusted analyses showed significantly higher risk of reoperation when the performing surgeon was born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo compared with the Sagittarius, see Table 2.
We performed subgroup analyses, investigating how lunar phases at the time of repair affected the risk of reoperation for each of the 12 surgeon zodiac signs. The waning moon was used as reference since it was the phase with the lowest reoperation rate, where all 12 surgeon zodiac signs were represented. The subgroup analyses (see Table 3) showed increased risk of reoperation after repairs performed by surgeons born under the Capricorn (HR 5.39) and Aquarius (HR 4.81) during the new compared with the waning moon. In addition, surgeons born under the Capricorn had an increased risk of reoperation (HR 9.13) during the full compared with the waning moon. Lastly, we found an increased risk of reoperation after repairs performed by surgeons born under the Pisces (HR 1.99) and Libra (HR 2.24) during the waxing compared with the waning moon.
Crude reoperation rate based on lunar phases seemed higher during the new (2.9%) and the waxing moon (2.5%) than during the waning (2.1%) and the full moon (2.0%). Table 4 shows the risk of reoperation after groin hernia repair in relation to the lunar phase on the day of the repair in the surgeon zodiac sign cohort. There was a significantly higher risk of reoperation after repairs performed during the new and the waxing moon compared with the waning moon.
The patient zodiac sign cohort included 151,901 groins hernia repairs, performed in 142,872 patients (see characteristics in Table 1). The median follow-up [IQR] was 93 [43–156] months. The crude reoperation rates were similar for all 12 patient zodiac signs (Appendix 1). Furthermore, there were no differences in the HRs amongst the different patient zodiac signs. The Cox regression was adjusted for patients’ sex, age, type of hernia, type of repair, and lunar phase (analyses not shown).
There were 20,406 repairs performed on regular Fridays and 675 repairs on a Friday that fell on the 13th of the month. The crude reoperation rate after repairs performed on Friday the 13th was 4.5% and 4.3% on regular Fridays (p͏=0.826).
Discussion
We found a significantly higher risk of reoperation after groin hernia repair performed by surgeons born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo compared with the Sagittarius. Repairs performed under the new or the waxing moon were associated with higher risk of reoperation compared with repairs performed under the waning moon, whereas patients’ zodiac sign or Friday the 13th did not affect the risk of reoperation.
Surgeon zodiac sign was a significant risk factor for reoperation after groin hernia repair, and we investigated whether the lunar phases could reduce the effect of the surgeons’ zodiac sign. This indicated that there was a significantly increased risk of reoperation during the full moon for surgeons born under the Capricorn and Aquarius. Furthermore, repairs performed by surgeons born under the Capricorn were associated with an increased risk of reoperation during the new moon. Surgeons born under the Pisces or Libra had higher risk of reoperation during the waxing moon. In the surgeon zodiac sign cohort, repairs performed during the waxing or the full moon were associated with a higher risk of reoperation compared with the waning moon. It could therefore be argued that surgeons could consider lunar phases when scheduling groin hernia repairs to minimise the risk of reoperation associated with the waxing moon. However, the moon is in the waxing phase approximately two weeks during every cycle of 29.5 days[[20]] and, thus difficult to avoid.
This study is an example of how statistical analyses can yield significant findings and the interpretation of such findings are key when distinguishing between random association and actual causality. We presented various analyses indicating that surgeons’ zodiac sign and lunar phases impacted the risk of reoperation after groin hernia repair. According to our data and analyses, one possible conclusion could be that surgeons born under the Sagittarius were better hernia surgeons than surgeons born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo. However, such a conclusion cannot be drawn without careful consideration: is it plausible that there is a cause-and-effect relation between the risk of reoperation after groin hernia repair and factors such as surgeons’ zodiac sign and lunar phase? To answer this question, we considered the aspect of causality. When assessing causality Bradford Hill’s nine criteria for causality are considered the golden standard.[[21]] Particularly, we will highlight the specificity, the plausibility, and the coherence of the evidence presented in this study. The specificity of our findings is difficult to quantify, but since there are many risk factors associated with the risk of reoperation after inguinal hernia repair,[[9–11]] it is likely that other factors could have affected the risk of reoperation, and thus the specificity of our findings is likely not high. Most health personnel would deem it biologically implausible that zodiac sign and lunar phase could affect the outcome of surgical interventions since zodiac sign and lunar phase are considered popular superstitions without supporting evidence. Furthermore, there are no biological pathways where factors such as zodiac sign or lunar phases are known to affect the outcome, and this assumption would seem contradictory to the bases of modern Western medicine. To our knowledge, only one previous study has investigated the impact of lunar phases and the short-term outcome after inguinal hernia repair and found that the lunar phase did not affect the risk of post-operative pain.[[22]] Other previous studies have investigated the impact of zodiac sign at the time of operation and the lunar phases on intraoperative blood loss,[[23]] various outcomes in radical cystectomy,[[24]] intracranial aneurysm rupture,[[25]] and elective spine surgery.[[26]] However, these results cannot be compared with our findings regarding groin hernia repair. Thus, there is no coherent evidence in the literature supporting the findings of the present study, and the findings presented here should be interpretated with caution before making conclusions regarding causality between zodiac sign, lunar phases and the risk of reoperation after groin hernia repair. Our findings should be interpreted as random associations rather than a cause-and-effect relationship, underlining that researchers, editors, peer reviewers, and readers should interpretate data analyses and statistical associations with caution. A conclusion regarding a cause-and-effect relation between celestial risk factors and groin hernia repair cannot be made solely based on the evidence presented in this study. That would require further studies, adding evidence to the cause-and-effect relationship.
This study has several methodological strengths. The Danish Hernia Database[[8]] and the Danish Patient Safety Authority's Online Register[[14]] both have nationwide coverage. Furthermore, the Danish Hernia Database draws data from the National Patient Registry,[[15]] ensuring a follow-up close to 100% in the Danish Hernia Database.[[8]] Data on lunar phases were obtained from the Copenhagen Planetarium’s Astronomy Department, ensuring high accuracy of the dates and times of the lunar phases. However, there are also limitations to this study. Data on the hernia defect size were not available in the majority (70%) of the included groins hernias and were therefore not reported. It is important to highlight the statistical analyses of the present study. We conducted several analyses with multiple variables. In theory, one in 20 analyses will coincidently result in a significant finding with a significance level of 0.05. This study included a large, representative sample size and we do not suspect a type II error in the patient zodiac sign cohort, where we did not find any significant effect of patients’ zodiac sign on the risk of reoperation. In the surgeon zodiac sign cohort, we found a significant effect of both surgeon zodiac sign and lunar phase on the risk of reoperation. It is possible that this significant finding was in fact a statistical type I error, thus falsely rejecting the null hypothesis. Furthermore, we conducted 62 Cox regressions (11 for patient zodiac sign, 11 for surgeon zodiac sign, 36 for the subgroup analyses for lunar phases in the surgeon zodiac sign cohort, and 3 for lunar phases alone), and we did not adjust for multiple testing, which again increased the risk of a type I error. Thus, the findings in this study may have statistical significance; however, the clinical significance is debatable, and the evidence presented in this study can be regarded as a random association as a result of statistical analyses with large sample sizes, and not necessarily a causal relation.
In conclusion, surgeons’ zodiac sign significantly affected the risk of reoperation after groin hernia repair, and surgeons born under the Sagittarius had a significantly lower risk of reoperation after groin hernia repair. The new and the waxing moon were associated with a significantly increased risk of reoperation. Patients’ zodiac sign or Friday the 13th did not affect the risk of reoperation. This study showed that it is relatively easy to find random associations in research with very large sample sizes, and it is important that findings, although statistically significant, should be considered with caution before concluding that there is a cause-and-effect relation.
View Appendix 1.
Summary
Abstract
Aim
We aimed to investigate how celestial phenomena like zodiac signs, lunar phases, and Friday the 13th impacted the risk of reoperation after groin hernia repair.
Method
We conducted a nationwide register-based study based on the Danish Hernia Database and Danish Patient Safety Authority’s Online Register between 2000–2019. We included patients ≥18 years undergoing open Lichtenstein or laparoscopic groin hernia repair. The main outcomes were risk of reoperation after groin hernia repair in relation to patient and surgeon zodiac sign, lunar phase at the time of the repair, and Friday the 13th vs other Fridays.
Results
151,901 groin hernias were included in the analysis of patient zodiac sign, and 25,075 groin hernias were included in the analysis of surgeon zodiac sign. Compared with the Sagittarius, there was a significantly higher risk of reoperation (HR [95% CI]) if the performing surgeon was born under the Capricorn (1.93 [1.16–3.12]); Pisces (1.68 [1.09–2.57]); Aries (1.61 [1.07–2.38]); Taurus (1.62 [1.04–2.54]); Cancer (2.21 [1.48–3.28]); or Virgo (1.71 [1.13–2.59]). Repairs performed under the waxing (1.23 [1.03–1.46]) and the new moon (1.54 [1.11–2.13]) had significantly higher risk of reoperation (HR [95% CI]) compared with the waning moon. Neither patient zodiac sign nor Friday the 13th affected risk of reoperation after groin hernia repair.
Conclusion
Surgeons’ zodiac sign and lunar phase significantly affected the risk of reoperation after groin hernia repair. Neither patients’ zodiac sign nor Friday the 13th influenced on the risk of reoperation after groin hernia repair. This indicates why significant findings should be considered carefully to distinguish between random statistical association and cause-and-effect relations.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
1) Webster D. The origin of the signs of the zodiac: an interpretation from the psychological viewpoint. American Imago. 1940; 1:31-47.
2) Montgomery SL. How the moon began: ideas of lunar reality in antiquity. In: The moon & the Western imagination. Tucson. University of Arizona Press; 1999. pp11-29.
3) Chakraborty U. Effects of different phases of the lunar month on humans. Biol Rhythm Res. 2014; 45:383-396.
4) Besley J, Hill D. Science and technology: public attitudes, knowledge, and interest [Internet]. Alexandria, Virginia, USA: National Center for Science and Engineering Statistics; May 2020 [cited 2022 Feb 9]. Available from: https://ncses.nsf.gov/pubs/nsb20207/public-familiarity-with-s-t-facts#pseudoscience.
5) Zarka P. Astronomy and astrology. Proc Int Astron Union. 2009;5:420-425.
6) Vyse SA. Believing in magic. In: Believing in magic: the psycology of superstition. New York. Oxford University Press; 2014. pp3-29.
7) Scanlon TJ, Luben RN, Scanlon FL, Singleton N. Is Friday the 13th bad for your health? BMJ. 1993; 307:1584-1586.
8) Friis-Andersen H, Bisgaard T. The Danish inguinal hernia database. Clin Epidemiol. 2016; 8:521-524.
9) Burcharth J, Pommergaard H-C, Bisgaard T, Rosenberg J. Patient-related risk factors for recurrence after inguinal hernia repair: a systematic review and meta-analysis of observational studies. Surg Innov. 2015; 22:303-317.
10) Schmedt CG, Sauerland S, Bittner R. Comparison of endoscopic procedures vs Lichtenstein and other open mesh techniques for inguinal hernia repair: a meta-analysis of randomized controlled trials. Surg Endosc. 2005; 19:188-199.
11) Zhong C, Wu B, Yang Z, et al. A meta-analysis comparing lightweight meshes with heavyweight meshes in Lichtenstein inguinal hernia repair. Surg Innov. 2013; 20:24-31.
12) Lewis JR. The astrology book: the encyclopedia of heavenly influences. Canton. Visible Ink Press; 2003.
13) Benchimol EI, Smeeth L, Guttmann A, et al. The REporting of studies Conducted using Observational Routinely-collected health Data (RECORD) Statement. PLoS Med. 2015; 12:e1001885.
14) Information about the Online register [Internet]. Denmark: Danish Patient Safety Authority. [cited 2022 Feb 9]. Available from: https://en.stps.dk/en/health-professionals-and-authorities/online-register-registered-health-professionals/information-about-the-online-register/.
15) Schmidt M, Schmidt SAJ, Sandegaard JL, Ehrenstein V, Pedersen L, Sørensen TH. The Danish National Patient Registry: a review of content, data quality, and research potential. Clin Epidemiol. 2015; 7:449-490.
16) Pedersen CB. The Danish Civil Registration System. Scand J Public Health. 2011; 39:22-25.
17) Andresen K, Friis-Andersen H, Rosenberg J. Laparoscopic repair of primary inguinal hernia performed in public hospitals or low-volume centers have increased risk of reoperation for recurrence. Surg Innov. 2016; 23:142-147.
18) Constellations and the Calendar [Internet]. NASA; Sep 2016 [cited 2022 Feb 9]. Available from: https://nasa.tumblr.com/post/150688852794/zodiac.
19) Horoscopes [Internet]. Ireland: Old Moore’s Almanac; 2019 [cited 2022 Feb 9]. Available from: https://oldmooresalmanac.com/horoscopes/.
20) Solar system exploration, Earth’s moon. Lunar phases and eclipses [Internet]. USA: NASA [cited 2022 Feb 9]. Available from: https://solarsystem.nasa.gov/moons/earths-moon/lunar-phases-and-eclipses/.
21) Bradford Hill A. The environment and disease: association or causation? Proc R Soc Med. 1965; 58:296-300.
22) Holzheimer R, Nitz C, Gresser U. Lunar phase does not influence surgical quality. Eur J Med Res. 2003; 8:414-418.
23) Schuld J, Slotta JE, Schuld S, Kollmar O, Schilling MK, Richter S. Popular belief meets surgical reality: impact of lunar phases, Friday the 13th and zodiac signs on emergency operations and intraoperative blood loss. World J Surg. 201; 35:1945-1949.
24) May M, Braun KP, Helke C, et al. Lunar phases and zodiac signs do not influence quality of radical cystectomy-a statistical analysis of 452 patients with invasive bladder cancer. Int Urol Nephrol. 2007; 39:1023-1030.
25) Bunevicius A, Gendvilaite A, Deltuva VP, Tamasauskas A. The association between lunar phase and intracranial aneurysm rupture: myth or reality? Own data and systematic review. BMC Neurol. 2017; 17:99.
26) Joswig H, Stienen MN, Hock C, Hildebrandt G, Surbeck W. The influence of lunar phases and zodiac sign ‘Leo’ on perioperative complications and outcome in elective spine surgery. Acta Neurochir. 2016; 158:1095-1101.
Contact diana@nzma.org.nz
for the PDF of this article
Celestial risk factors in groin hernia repair and random statistical association: a nationwide register-based study
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Celestial phenomena like lunar phases and zodiac signs have been part of human culture since ancient times.[[1,2]] Many still believe that both zodiac signs and lunar phases influence daily life and to some extent even health.[[3,4]] However, these beliefs are often regarded as being superstitions without scientific evidence.[[5]] Nevertheless, zodiac signs and lunar phases are attributed significant meaning and value in daily life,[[5]] and many believe celestial factors carry significant attributes regarding health.[[6]] Additionally, there are ill-fated beliefs surrounding Friday the 13th, some say it is an “unlucky” day and some even believe it is an omen of death.[[7]]
The Danish Hernia Database provides data on almost all groin hernia repairs performed in Denmark with approximately 100% follow-up,[[8]] making it possible to assess the long-term effect of lunar phases, zodiac signs, and Friday the 13th on reoperation rate after groin hernia repair. There are many known patient-related and procedure-related risk factors for reoperation after groin hernia repair.[[9–11]] However, the impact of celestial-related risk factors have not previously been investigated.
We wished to investigate if it was possible to find an association between celestial phenomena and the reoperation rate after groin hernia repair. This study aimed to investigate how the 12 zodiac signs from Western astrology,[[12]] lunar phases, and Friday the 13th impacted the risk of reoperation after groin hernia repair.
Methods
We performed a register-based cohort study with nationwide prospectively collected data on groin hernia repairs which followed the REporting of studies Conducted using Observational Routinely collected health Data (RECORD) statement.[[13]] Data were obtained from the Danish Hernia Database[[8]] and the Danish Patient Safety Authority’s Online Register.[[14]] Data from the two databases were linked via surgeons’ unique authorisation IDs. The Danish Hernia Database contains data on patients’ sex, age, birthdate, (used to obtain patients’ zodiac sign), and date of operation (used to obtain the lunar phase at the time of operation). Furthermore, the Danish Hernia Database contains perioperative data such as side of the hernia, whether the repair was primary or recurrent, elective or emergency, type of hernia, and method of repair: Lichtenstein or laparoscopic TransAbdominal PrePeritoneal (TAPP) repair. The Danish Hernia Database also draws data from the Danish National Patient Registry[[15]] and the Danish Civil Registration System,[[16]] providing data on reoperation status, emigration, and deaths. The Danish Patient Safety Authority's Online Register contains data on all surgeons registered in Denmark such as surgeons’ authorisation ID,[[14]] which was included in the Danish Hernia Database from 2011, and the surgeons’ date of birth, making it possible to determine the surgeons’ zodiac sign.
Patients were included between January 2000 and December 2019. Recurrent groin hernia repair was defined as an operation for a new hernia on the same side as a previous repair. Since the same patient could be operated for a groin hernia on both sides, either at the same time or independently, we considered groins for inclusion rather than patients. This also ensured that a recurrent hernia was in fact on the same side as a previous hernia. Patients were followed until death, reoperation, or the end of the study period (1 January 2020).
Eligibility criteria for inclusion were primary groin hernia repairs performed in patients ≥18 years with either Lichtenstein or laparoscopic TAPP repair. TAPP technique accounts for >98% of laparoscopic repairs in Denmark,[[17]] therefore other laparoscopic approaches were not included. Both elective and emergency repairs were included. Groin hernias were considered primary if the repair was registered as a primary repair. Furthermore, we performed a “look back” for each groin from 1998 for previous repairs to identify recurrent hernias. Groin hernias were excluded if the first registered operation was a reoperation, the type of hernia was not registered, the repair was performed before 2000, or if patients had either emigrated or were living outside of Denmark. The inclusion criterion for surgeons was a valid authorisation ID entry. Surgeons were excluded if the authorisation ID was registered ≤2 times. The groin hernias were divided into two overlapping cohorts and analysed separately: one cohort with patients’ zodiac sign as the variable and one cohort with the surgeons’ zodiac sign as the variable.
The outcomes were risk of reoperation after groin hernia repair in relation to surgeons’ zodiac sign, patients’ zodiac sign, lunar phase at the time of repair, and whether the repair was performed on Friday the 13th vs other Fridays. The 12 zodiac signs used were from Western astrology based on the tropical zodiac.[[12]] The zodiac signs used in Western astrology originates from the ancient Babylonians who mapped the zodiac approximately 3,000 years ago.[[18]] Zodiac signs were assigned to the included surgeons and patients based on their birthdate.[[19]] In Western astrology, there are 12 signs: Capricorn, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio and Sagittarius. During a lunar cycle, the moon passes through four phases: the new, the waxing, the waning, and the full moon.[[20]] Data on lunar phases at the time of the repair (2000–2019) were obtained from the Copenhagen Planetarium’s Astronomy Department via personal contact. The day of the repair was assessed according to the Gregorian calendar which was used to identify Friday the 13th and other Fridays.
Subgroup analyses were performed to investigate the impact of lunar phases on the risk of reoperation for each surgeon zodiac sign. The reference for the subgroup analyses was the lunar phase with the lowest reoperation rate where all 12 surgeon zodiac signs were represented.
The statistical analyses were performed with SPSS (version 25.0, IBM, Armonk, NY, USA). Q-Q-plots and histograms were used to evaluate the distribution of data. Normally distributed, continuous data were presented as mean with standard deviation (SD), while non-normally distributed, continuous data were presented as median with interquartile range [IQR]. Categorical data were presented as crude reoperation rates and tested with the Chi-squared test. The difference in distribution of zodiac signs within groups was evaluated with 95% confidence intervals (CIs). Cox proportional hazard analyses was used to assess the risk of reoperation in relation to zodiac signs and lunar phases. The analyses were adjusted for patients’ sex, age, hernia type, and type of repair. Furthermore, the analyses for zodiac signs were adjusted for lunar phases while the analyses for lunar phases were adjusted for surgeons’ zodiac sign. The group with the lowest reoperation rate was used as reference. Risk of reoperation was presented as hazard ratios (HR) with 95% CIs. Findings were considered significant when p≤0.05.
Approval for this study was obtained from the Danish Data Protection Agency (P-2020-380). According to Danish law, approval from ethics committees and written informed consent were not required to conduct this study.
Results
In the surgeon zodiac sign cohort, we included 25,075 groin hernia repairs performed in 2011–2019. In the patient zodiac sign cohort, 151,901 groin hernia repairs were included between 2000–2019. The selection process of groin hernias in patients is shown in Figure 1.
View Figures & Tables.
The patient demographic and operative characteristics for the surgeon zodiac sign cohort and patient zodiac sign cohort are shown in Table 1.
The surgeon zodiac sign cohort included 541 surgeons, performing 25,075 repairs in 22,916 patients (see characteristics in Table 1). Of these repairs, 4%, 15%, and 5% were performed by surgeons born under the Capricorn, Aries and Scorpio, respectively, which differed significantly from the other surgeon zodiac signs. Among the 541 included surgeons, the 12 zodiac signs were evenly distributed (data not shown). The median follow-up [IQR] was 23 (12–33) months. The crude reoperation rates after groin hernia repair for each surgeon zodiac sign are shown in Figure 2.
The adjusted risk of reoperation after groin hernia repair based on surgeons’ zodiac sign is shown in Table 2. Surgeons born under the Sagittarius were used as reference since they had the lowest crude reoperation rate (1.5%). The adjusted analyses showed significantly higher risk of reoperation when the performing surgeon was born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo compared with the Sagittarius, see Table 2.
We performed subgroup analyses, investigating how lunar phases at the time of repair affected the risk of reoperation for each of the 12 surgeon zodiac signs. The waning moon was used as reference since it was the phase with the lowest reoperation rate, where all 12 surgeon zodiac signs were represented. The subgroup analyses (see Table 3) showed increased risk of reoperation after repairs performed by surgeons born under the Capricorn (HR 5.39) and Aquarius (HR 4.81) during the new compared with the waning moon. In addition, surgeons born under the Capricorn had an increased risk of reoperation (HR 9.13) during the full compared with the waning moon. Lastly, we found an increased risk of reoperation after repairs performed by surgeons born under the Pisces (HR 1.99) and Libra (HR 2.24) during the waxing compared with the waning moon.
Crude reoperation rate based on lunar phases seemed higher during the new (2.9%) and the waxing moon (2.5%) than during the waning (2.1%) and the full moon (2.0%). Table 4 shows the risk of reoperation after groin hernia repair in relation to the lunar phase on the day of the repair in the surgeon zodiac sign cohort. There was a significantly higher risk of reoperation after repairs performed during the new and the waxing moon compared with the waning moon.
The patient zodiac sign cohort included 151,901 groins hernia repairs, performed in 142,872 patients (see characteristics in Table 1). The median follow-up [IQR] was 93 [43–156] months. The crude reoperation rates were similar for all 12 patient zodiac signs (Appendix 1). Furthermore, there were no differences in the HRs amongst the different patient zodiac signs. The Cox regression was adjusted for patients’ sex, age, type of hernia, type of repair, and lunar phase (analyses not shown).
There were 20,406 repairs performed on regular Fridays and 675 repairs on a Friday that fell on the 13th of the month. The crude reoperation rate after repairs performed on Friday the 13th was 4.5% and 4.3% on regular Fridays (p͏=0.826).
Discussion
We found a significantly higher risk of reoperation after groin hernia repair performed by surgeons born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo compared with the Sagittarius. Repairs performed under the new or the waxing moon were associated with higher risk of reoperation compared with repairs performed under the waning moon, whereas patients’ zodiac sign or Friday the 13th did not affect the risk of reoperation.
Surgeon zodiac sign was a significant risk factor for reoperation after groin hernia repair, and we investigated whether the lunar phases could reduce the effect of the surgeons’ zodiac sign. This indicated that there was a significantly increased risk of reoperation during the full moon for surgeons born under the Capricorn and Aquarius. Furthermore, repairs performed by surgeons born under the Capricorn were associated with an increased risk of reoperation during the new moon. Surgeons born under the Pisces or Libra had higher risk of reoperation during the waxing moon. In the surgeon zodiac sign cohort, repairs performed during the waxing or the full moon were associated with a higher risk of reoperation compared with the waning moon. It could therefore be argued that surgeons could consider lunar phases when scheduling groin hernia repairs to minimise the risk of reoperation associated with the waxing moon. However, the moon is in the waxing phase approximately two weeks during every cycle of 29.5 days[[20]] and, thus difficult to avoid.
This study is an example of how statistical analyses can yield significant findings and the interpretation of such findings are key when distinguishing between random association and actual causality. We presented various analyses indicating that surgeons’ zodiac sign and lunar phases impacted the risk of reoperation after groin hernia repair. According to our data and analyses, one possible conclusion could be that surgeons born under the Sagittarius were better hernia surgeons than surgeons born under the Capricorn, Pisces, Aries, Taurus, Cancer, or Virgo. However, such a conclusion cannot be drawn without careful consideration: is it plausible that there is a cause-and-effect relation between the risk of reoperation after groin hernia repair and factors such as surgeons’ zodiac sign and lunar phase? To answer this question, we considered the aspect of causality. When assessing causality Bradford Hill’s nine criteria for causality are considered the golden standard.[[21]] Particularly, we will highlight the specificity, the plausibility, and the coherence of the evidence presented in this study. The specificity of our findings is difficult to quantify, but since there are many risk factors associated with the risk of reoperation after inguinal hernia repair,[[9–11]] it is likely that other factors could have affected the risk of reoperation, and thus the specificity of our findings is likely not high. Most health personnel would deem it biologically implausible that zodiac sign and lunar phase could affect the outcome of surgical interventions since zodiac sign and lunar phase are considered popular superstitions without supporting evidence. Furthermore, there are no biological pathways where factors such as zodiac sign or lunar phases are known to affect the outcome, and this assumption would seem contradictory to the bases of modern Western medicine. To our knowledge, only one previous study has investigated the impact of lunar phases and the short-term outcome after inguinal hernia repair and found that the lunar phase did not affect the risk of post-operative pain.[[22]] Other previous studies have investigated the impact of zodiac sign at the time of operation and the lunar phases on intraoperative blood loss,[[23]] various outcomes in radical cystectomy,[[24]] intracranial aneurysm rupture,[[25]] and elective spine surgery.[[26]] However, these results cannot be compared with our findings regarding groin hernia repair. Thus, there is no coherent evidence in the literature supporting the findings of the present study, and the findings presented here should be interpretated with caution before making conclusions regarding causality between zodiac sign, lunar phases and the risk of reoperation after groin hernia repair. Our findings should be interpreted as random associations rather than a cause-and-effect relationship, underlining that researchers, editors, peer reviewers, and readers should interpretate data analyses and statistical associations with caution. A conclusion regarding a cause-and-effect relation between celestial risk factors and groin hernia repair cannot be made solely based on the evidence presented in this study. That would require further studies, adding evidence to the cause-and-effect relationship.
This study has several methodological strengths. The Danish Hernia Database[[8]] and the Danish Patient Safety Authority's Online Register[[14]] both have nationwide coverage. Furthermore, the Danish Hernia Database draws data from the National Patient Registry,[[15]] ensuring a follow-up close to 100% in the Danish Hernia Database.[[8]] Data on lunar phases were obtained from the Copenhagen Planetarium’s Astronomy Department, ensuring high accuracy of the dates and times of the lunar phases. However, there are also limitations to this study. Data on the hernia defect size were not available in the majority (70%) of the included groins hernias and were therefore not reported. It is important to highlight the statistical analyses of the present study. We conducted several analyses with multiple variables. In theory, one in 20 analyses will coincidently result in a significant finding with a significance level of 0.05. This study included a large, representative sample size and we do not suspect a type II error in the patient zodiac sign cohort, where we did not find any significant effect of patients’ zodiac sign on the risk of reoperation. In the surgeon zodiac sign cohort, we found a significant effect of both surgeon zodiac sign and lunar phase on the risk of reoperation. It is possible that this significant finding was in fact a statistical type I error, thus falsely rejecting the null hypothesis. Furthermore, we conducted 62 Cox regressions (11 for patient zodiac sign, 11 for surgeon zodiac sign, 36 for the subgroup analyses for lunar phases in the surgeon zodiac sign cohort, and 3 for lunar phases alone), and we did not adjust for multiple testing, which again increased the risk of a type I error. Thus, the findings in this study may have statistical significance; however, the clinical significance is debatable, and the evidence presented in this study can be regarded as a random association as a result of statistical analyses with large sample sizes, and not necessarily a causal relation.
In conclusion, surgeons’ zodiac sign significantly affected the risk of reoperation after groin hernia repair, and surgeons born under the Sagittarius had a significantly lower risk of reoperation after groin hernia repair. The new and the waxing moon were associated with a significantly increased risk of reoperation. Patients’ zodiac sign or Friday the 13th did not affect the risk of reoperation. This study showed that it is relatively easy to find random associations in research with very large sample sizes, and it is important that findings, although statistically significant, should be considered with caution before concluding that there is a cause-and-effect relation.
View Appendix 1.
Summary
Abstract
Aim
We aimed to investigate how celestial phenomena like zodiac signs, lunar phases, and Friday the 13th impacted the risk of reoperation after groin hernia repair.
Method
We conducted a nationwide register-based study based on the Danish Hernia Database and Danish Patient Safety Authority’s Online Register between 2000–2019. We included patients ≥18 years undergoing open Lichtenstein or laparoscopic groin hernia repair. The main outcomes were risk of reoperation after groin hernia repair in relation to patient and surgeon zodiac sign, lunar phase at the time of the repair, and Friday the 13th vs other Fridays.
Results
151,901 groin hernias were included in the analysis of patient zodiac sign, and 25,075 groin hernias were included in the analysis of surgeon zodiac sign. Compared with the Sagittarius, there was a significantly higher risk of reoperation (HR [95% CI]) if the performing surgeon was born under the Capricorn (1.93 [1.16–3.12]); Pisces (1.68 [1.09–2.57]); Aries (1.61 [1.07–2.38]); Taurus (1.62 [1.04–2.54]); Cancer (2.21 [1.48–3.28]); or Virgo (1.71 [1.13–2.59]). Repairs performed under the waxing (1.23 [1.03–1.46]) and the new moon (1.54 [1.11–2.13]) had significantly higher risk of reoperation (HR [95% CI]) compared with the waning moon. Neither patient zodiac sign nor Friday the 13th affected risk of reoperation after groin hernia repair.
Conclusion
Surgeons’ zodiac sign and lunar phase significantly affected the risk of reoperation after groin hernia repair. Neither patients’ zodiac sign nor Friday the 13th influenced on the risk of reoperation after groin hernia repair. This indicates why significant findings should be considered carefully to distinguish between random statistical association and cause-and-effect relations.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
1) Webster D. The origin of the signs of the zodiac: an interpretation from the psychological viewpoint. American Imago. 1940; 1:31-47.
2) Montgomery SL. How the moon began: ideas of lunar reality in antiquity. In: The moon & the Western imagination. Tucson. University of Arizona Press; 1999. pp11-29.
3) Chakraborty U. Effects of different phases of the lunar month on humans. Biol Rhythm Res. 2014; 45:383-396.
4) Besley J, Hill D. Science and technology: public attitudes, knowledge, and interest [Internet]. Alexandria, Virginia, USA: National Center for Science and Engineering Statistics; May 2020 [cited 2022 Feb 9]. Available from: https://ncses.nsf.gov/pubs/nsb20207/public-familiarity-with-s-t-facts#pseudoscience.
5) Zarka P. Astronomy and astrology. Proc Int Astron Union. 2009;5:420-425.
6) Vyse SA. Believing in magic. In: Believing in magic: the psycology of superstition. New York. Oxford University Press; 2014. pp3-29.
7) Scanlon TJ, Luben RN, Scanlon FL, Singleton N. Is Friday the 13th bad for your health? BMJ. 1993; 307:1584-1586.
8) Friis-Andersen H, Bisgaard T. The Danish inguinal hernia database. Clin Epidemiol. 2016; 8:521-524.
9) Burcharth J, Pommergaard H-C, Bisgaard T, Rosenberg J. Patient-related risk factors for recurrence after inguinal hernia repair: a systematic review and meta-analysis of observational studies. Surg Innov. 2015; 22:303-317.
10) Schmedt CG, Sauerland S, Bittner R. Comparison of endoscopic procedures vs Lichtenstein and other open mesh techniques for inguinal hernia repair: a meta-analysis of randomized controlled trials. Surg Endosc. 2005; 19:188-199.
11) Zhong C, Wu B, Yang Z, et al. A meta-analysis comparing lightweight meshes with heavyweight meshes in Lichtenstein inguinal hernia repair. Surg Innov. 2013; 20:24-31.
12) Lewis JR. The astrology book: the encyclopedia of heavenly influences. Canton. Visible Ink Press; 2003.
13) Benchimol EI, Smeeth L, Guttmann A, et al. The REporting of studies Conducted using Observational Routinely-collected health Data (RECORD) Statement. PLoS Med. 2015; 12:e1001885.
14) Information about the Online register [Internet]. Denmark: Danish Patient Safety Authority. [cited 2022 Feb 9]. Available from: https://en.stps.dk/en/health-professionals-and-authorities/online-register-registered-health-professionals/information-about-the-online-register/.
15) Schmidt M, Schmidt SAJ, Sandegaard JL, Ehrenstein V, Pedersen L, Sørensen TH. The Danish National Patient Registry: a review of content, data quality, and research potential. Clin Epidemiol. 2015; 7:449-490.
16) Pedersen CB. The Danish Civil Registration System. Scand J Public Health. 2011; 39:22-25.
17) Andresen K, Friis-Andersen H, Rosenberg J. Laparoscopic repair of primary inguinal hernia performed in public hospitals or low-volume centers have increased risk of reoperation for recurrence. Surg Innov. 2016; 23:142-147.
18) Constellations and the Calendar [Internet]. NASA; Sep 2016 [cited 2022 Feb 9]. Available from: https://nasa.tumblr.com/post/150688852794/zodiac.
19) Horoscopes [Internet]. Ireland: Old Moore’s Almanac; 2019 [cited 2022 Feb 9]. Available from: https://oldmooresalmanac.com/horoscopes/.
20) Solar system exploration, Earth’s moon. Lunar phases and eclipses [Internet]. USA: NASA [cited 2022 Feb 9]. Available from: https://solarsystem.nasa.gov/moons/earths-moon/lunar-phases-and-eclipses/.
21) Bradford Hill A. The environment and disease: association or causation? Proc R Soc Med. 1965; 58:296-300.
22) Holzheimer R, Nitz C, Gresser U. Lunar phase does not influence surgical quality. Eur J Med Res. 2003; 8:414-418.
23) Schuld J, Slotta JE, Schuld S, Kollmar O, Schilling MK, Richter S. Popular belief meets surgical reality: impact of lunar phases, Friday the 13th and zodiac signs on emergency operations and intraoperative blood loss. World J Surg. 201; 35:1945-1949.
24) May M, Braun KP, Helke C, et al. Lunar phases and zodiac signs do not influence quality of radical cystectomy-a statistical analysis of 452 patients with invasive bladder cancer. Int Urol Nephrol. 2007; 39:1023-1030.
25) Bunevicius A, Gendvilaite A, Deltuva VP, Tamasauskas A. The association between lunar phase and intracranial aneurysm rupture: myth or reality? Own data and systematic review. BMC Neurol. 2017; 17:99.
26) Joswig H, Stienen MN, Hock C, Hildebrandt G, Surbeck W. The influence of lunar phases and zodiac sign ‘Leo’ on perioperative complications and outcome in elective spine surgery. Acta Neurochir. 2016; 158:1095-1101.
Contact diana@nzma.org.nz
for the PDF of this article
Celestial risk factors in groin hernia repair and random statistical association: a nationwide register-based study
Celestial phenomena like lunar phases and zodiac signs have been part of human culture since ancient times. Many still believe that both zodiac signs and lunar phases influence daily life and to some extent even health.
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