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Obesity is a major problem in New Zealand with the direct-care costs estimated at $460 million.1 Although the growth of obesity may be slowing, its prevalence remains high (26.5%) and 9.1% of the population are morbidly obese.2 Obesity is associated with increased risk of mortality from cardiovascular disease and some cancers, a higher incidence of numerous conditions including diabetes, hypertension, joint disorders and obstructive sleep apnoea.3Bariatric surgery is a safe and effective way of managing morbid obesity for selected individuals and a recommended approach in the New Zealand guidelines for weight management.3,4 Weight associated comorbidities frequently resolve after bariatric procedures.5Bariatric surgery has been offered by the Auckland District Health Board (ADHB) since 2008. Mainly Roux-en-Y gastric bypass or sleeve gastrectomies are carried out. The effect of bariatric surgery on clinical outcomes has been investigated in New Zealand,6 but no estimate of the effect of the surgery on patient-oriented outcomes has been reported in New Zealand.The ADHB Bariatric Service has been routinely collecting self-reported perceived health using the SF-36 and this data offered the opportunity to measure the impact of bariatric surgery on the patient's perception of their health-related quality of life (HRQoL).Methods Background—The ADHB Bariatric Service has selection criteria for bariatric surgery aligned with that proposed by the National Institute of Health.7 Patients must be aged between 18 and 60 years, have a body mass index of greater than 40 kg/m2, or greater than 35 kg/m2 with obesity-related comorbidity, and have been obese for more than five years with failed non-surgical attempts at weight loss. The Service is not available if a patient's weight is greater than 170 kg or their body mass index (BMI) of is greater than 55 kg/m2 or if they are considered a high operative risk due to end stage disease. Participants and study design—An audit was carried out at Auckland District Health Board (ADHB) between January and December 2010. Participants were included in the audit if they met the above selection criteria for bariatric surgery and had completed baseline questionnaires prior to bariatric surgery at any time forward from December 2008 to December 2010. Participants completed the baseline questionnaire at a pre-operative information seminar and returned this at their first pre-operative clinic visit. Following a bariatric intervention patient's repeated the SF-36 questionnaire post-procedure at their 6-month follow-up clinic appointment through to the end of the audit period. The Northern Regional Ethics Committee X approved the audit (NTX/10/01/EXP/001). The SF-36 is a widely used generic instrument to measure HRQoL. The SF-36 contains 36 questions, 35 of which measure perceived health using a 0-100 scale across eight domains - physical functioning, role limitations due to physical functioning, bodily pain, general health, vitality, social functioning, role limitation due to emotional problems and mental health and the last item measures health transition, which is not reported here.8 Higher scores reflect better perceived health, with 100 being the best possible score for a domain. The eight domains can also be summarised into two component summary scores, namely the physical and mental component summary scores (PCS and MCS respectively).9 Both scores were normalised to have a mean of 50 and a standard deviation of 10. Scores below 50 represent scores below the population mean. As the standard deviation is 10, each point below 50 represents 0.1 of a standard deviation. Statistical analyses—Student's paired t-test was used to examine differences between matched pairs, with statistical significance set at 5%. Missing data were handled as per standard procedures.10 Briefly, where greater than 50% of items in a multi-question domain (e.g. role physical and vitality) were answered, a person specific estimate or average score of completed questions within the same domain was used. To assess the size of any changes between baseline and post-procedure scores at 6 months, standardised response means (SRM) were calculated. SRMs are the change in outcome divided by the standard deviation of the change and thus remove the noise of variance of the change leaving only the signal. Cohen's criteria for effect sizes were utilised when assessing the size of the SRMs.11 SRMs of greater than 0.8 were considered large, 0.5 to 0.79 were considered moderate, 0.2 to 0.49 were considered small and SRMs less than 0.2 were considered trivial.12 All analyses were carried out in SPSS (version 18) software. Results Forty patients completed baseline SF-36 questionnaires prior to bariatric surgery. Twelve patients had either not received bariatric surgery or had not completed the 6 month follow up by the end of the audit period. Twenty-eight patients underwent bariatric surgery and completed SF-36 questionnaires at 6 months post-procedure during the audit period. Twenty-three patients underwent laparoscopic Roux-en-Y gastric bypass and five underwent laparoscopic sleeve gastrectomy. These patients were predominantly New Zealand European, female, and class III obese (Table 1). Fifteen patients were diabetic. Table 1. Patient characteristics and comorbidities at baseline and 6 months after the bariatric procedure Variables Baseline 6 months Number (%) Number (%) Age (mean, SD) 42.8 (9.9) Female 22 (78.6) Ethnicity NZ European/Other Maori Pacific Asian 19 (67.8) 4 (14.3) 3 (10.7) 2 (7.1) Weight (kg, mean, SD) 131.2 (19.6) 94.4 (13.6) BMI (kg/m2, mean, SD) 45.3 (6.1) 32.6 (4.1) Obesity class Overweight Class I (BMI 30-34.99) Class II (BMI 35-39.99) Class III (BMI ≥40) - 1 (3.6) 4 (14.3) 23 (82.1) 12 (42.9) 6 (21.4) 2 (7.1) 8 (28.6) Type 2 diabetes mellitus Diet controlled - 1 (3.6) Oral hypoglycaemics 12 (42.9) 2 (7.1) Insulin 3 (10.7) 1 (3.6) The mean SF-36 domain and component summary scores are provided in Table 2. The baseline PCS and MCS reflect scores well below the population norms. There was significant improvement in all SF-36 scores across all domains at 6 months. The mean differences ranged from a low of 15.3 on the mental health domain to a high of 45.8 in the general health domain. The change in the PCS would indicate that the patients moved from scores 1.5 standard deviations below the population mean prior to surgery to the population mean 6 months after surgery. The change in the MCS was not as dramatic, but still represents a shift of one standard deviation to slightly better than the population mean 6 months after the surgery. Table 2. Difference between SF-36 domain scores at baseline and 6 months after bariatric procedure (n=28) Domain Baseline 6 months Mean difference (95% CI) P value Mean Mean Physical functioning 53.1 86.1 33.0 (21.4-44.6) <0.001 Role physical 45.5 81.3 35.7 (15.4-56.1) 0.001 Bodily pain 45.5 77.1 31.6 (20.0-43.3) <0.001 General health 41.5 84.6 45.8 (37.0-54.6) <0.001 Vitality 38.8 72.9 34.1 (24.8-43.4) <0.001 Social functioning 58.9 87.1 28.1 (17.0-39.2) <0.001 Role emotional 67.9 83.3 17.3 (2.5-32.1) 0.024 Mental health 67.4 82.7 15.3 (7.3-23.2) 0.001 PCS 36.0 50.1 15.3 (10.3-20.2) <0.001 MCS 42.5 52.8 12.9 (8.2-17.7) <0.001 PCS = Physical Component Summary score, MCS = Mental Component Summary score. The SRMs for the mean differences were between 0.5 for the role emotional domain to 2.2 for the general health domain (Table 3). Although the change in the role physical, role emotional and mental health domains is a moderate sized change, the change in the remaining five domains is large. As would be expected from the large changes in some of the constituent scores, the changes in the PCS and MCS scores could also be considered large. Table 3. Standardised response means to measure size of change SF-36 Health Related Quality of Life Domain Mean difference SE SRM Effect Physical functioning 33.0 5.7 1.1 Large Role physical 35.7 9.9 0.7 Moderate Bodily pain 31.6

Summary

Abstract

Aim

To explore the impact of bariatric surgery on health-related quality of life (HRQoL).

Method

An audit of patients referred for bariatric procedures. Patients completed Short Form-36 questionnaires at their first pre-operative clinic and at their 6-month follow up appointment after surgery. SF-36 scores were compared with standard parametric tests.

Results

40 patients completed baseline SF-36 questionnaires and underwent bariatric surgery, 28 were surveyed again 6 months post-procedure during the audit period between December 2008 and December 2010. Twenty-three patients underwent laparoscopic Roux-en-Y gastric bypass and five underwent laparoscopic sleeve gastrectomy. The patients were predominantly New Zealand European, female, with a body mass index greater than 40 kg/m2. Significant improvements in health-related quality of life were observed. The physical and mental component summary scores were initially well below the population norms, but increased to the norm 6 months after surgery.

Conclusion

The HRQoL of morbidly obese patients significantly improves after bariatric surgery. Services including the SF-36 in their measurement armamentarium can demonstrate the Services impact on patient- perceived outcomes in addition to clinically-focused outcomes.

Author Information

Briar McLeod, Parenteral Nutrition Clinical Nurse Specialist, Auckland District Health Board; Grant Beban, Consultant Surgeon, Auckland District Health Board; Jill Sanderson, Upper Gastrointestinal Clinical Nurse Specialist, Auckland District Health Board; Ann McKillop, Senior Lecturer, School of Nursing, University of Auckland; Andrew Jull, Associate Professor, School of Nursing and Senior Research Fellow, Clinical Trials Research Unit, School of Population Health, University of Auckland

Acknowledgements

Correspondence

Briar McLeod, PN Clinical Nurse Specialist, Auckland District Health Board, Private Bag 92024, Auckland, New Zealand. Fax: +64 (0)9 3754334

Correspondence Email

briarmcl@adhb.govt.nz

Competing Interests

None known.

Ministry of Health. Body Size Technical Report: Measurements and classifications in the 2006/07 New Zealand Health Survey. Wellington: Ministry of Health, 2008.Ministry of Health. A portrait of health. Key results of the 2006/07 New Zealand health survey. Wellington: Ministry of Health, 2008.Ministry of Health, Clinical Trials Research Unit. Clinical Guidelines for Weight Management in New Zealand Adults. Wellington: Ministry of Health, 2009.Jull A, Lawes CMM, Eyles H, et al. Clinical guidelines for weight management in New Zealand adults, children and young people. J Prim Health Care 2011;3(1):66-71.Sjostrom L, Lindroos AK, Peltonen M, et al. Lifestyle, diabetes, and cardiovascular risk factors 10 years after bariatric surgery. N Engl J Med 2004;351(26):2683-93.He M, Stubbs R. Gastric bypass surgery for severe obesity: what can be achieved? NZ Med J 2004;117(1207):1-14.Consensus Development Conference Panel. NIH Conference Gastrointestinal surgery for severe obesity. Ann Intern Med 1991;115(12):956-61.Ware J, Snow K, Kosinski M, Gandek B. SF-36 Health Survey: manual & interpretation guide. Boston: Nimrod Press, 1993.Ware JE, Kosinki M, Keller SD. SF-36 physical and mental health summary scores: a user's manual. Boston: The Health Institute, 1994.Ware JE, Snow KK, Kosinski M, Gandek MS. SF-36 Health survey: manual and interpretation guide. Lincoln: QualityMetric Incorporated, 2000.Cohen J. Statistical power analysis for the behavioral sciences. 2nd ed. Hillsdale, New Jersey: Lawrence Erlbaum Associates Incorporated, 1988.Hays RD, Farivar SS, Liu H. Approaches and recommendations for estimating a minimally important differences for health-related quality of life measures. J Chronic Obstruct Pulmon Dis 2005;2:63-7.Ni Mhurchu C, Bennett D, Lin R, et al. Obesity and health-related quality of life: results from a weight loss trial. NZ Med J 2004;117(1207):1-9.van Nunen AM, Wouters EJ, Vingerhoets AJ, et al. The health-related quality of life of obese persons seeking or not seeking surgical or non-surgical treatment: a meta-analysis. Obes Surg 2007;17:1357-66.Rea JD, Yarbrough DE, Leeth RR, et al. Influence of complications and extent of weight loss on quality of life after laparoscopic Roux-en-Y gastric bypass. Surg Endosc 2007;21(7):1095-100.van Hout GC, Fortuin FA, Pelle AJ, et al. Health-related quality of life following vertical banded gastroplasty. Surg Endosc 2009;23(3):550-6.Nguyen NT, Slone JA, Nguyen XT, et al. A prospective randomised trial of laparoscopic gastric bypass versus laparoscopic adjustable gastric banding for the treatment of morbid obesity. Ann Surg 2009;250(4):631-41.Kolotkin RL, Crosby RD, Gress RE, et al. Two-year changes in health-related quality of life in gastric bypass patients compared with severely obese controls. Surg Obes Relat Dis 2009;5(2):250-6.Dixon JB, Dixon ME, O'Brien PE. Quality of life after lap-band placement: influence of time, weight loss, and comorbidities. Obes Res 2001;9(11):713--21.Karlsson J, Taft C, Ryden A, et al. Ten-year trends in health-related quality of life after surgical and conventional treatment for severe obesity: the SOS intervention study. Int J Obes 2007;31(8):1248-61.Husted JA, Cook RJ, Farewell VT, Galdman DD. Methods for assessing responsiveness: a critical review and recommendations J Clin Epidemiol 2000;53(5):459-68.

For the PDF of this article,
contact nzmj@nzma.org.nz

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Obesity is a major problem in New Zealand with the direct-care costs estimated at $460 million.1 Although the growth of obesity may be slowing, its prevalence remains high (26.5%) and 9.1% of the population are morbidly obese.2 Obesity is associated with increased risk of mortality from cardiovascular disease and some cancers, a higher incidence of numerous conditions including diabetes, hypertension, joint disorders and obstructive sleep apnoea.3Bariatric surgery is a safe and effective way of managing morbid obesity for selected individuals and a recommended approach in the New Zealand guidelines for weight management.3,4 Weight associated comorbidities frequently resolve after bariatric procedures.5Bariatric surgery has been offered by the Auckland District Health Board (ADHB) since 2008. Mainly Roux-en-Y gastric bypass or sleeve gastrectomies are carried out. The effect of bariatric surgery on clinical outcomes has been investigated in New Zealand,6 but no estimate of the effect of the surgery on patient-oriented outcomes has been reported in New Zealand.The ADHB Bariatric Service has been routinely collecting self-reported perceived health using the SF-36 and this data offered the opportunity to measure the impact of bariatric surgery on the patient's perception of their health-related quality of life (HRQoL).Methods Background—The ADHB Bariatric Service has selection criteria for bariatric surgery aligned with that proposed by the National Institute of Health.7 Patients must be aged between 18 and 60 years, have a body mass index of greater than 40 kg/m2, or greater than 35 kg/m2 with obesity-related comorbidity, and have been obese for more than five years with failed non-surgical attempts at weight loss. The Service is not available if a patient's weight is greater than 170 kg or their body mass index (BMI) of is greater than 55 kg/m2 or if they are considered a high operative risk due to end stage disease. Participants and study design—An audit was carried out at Auckland District Health Board (ADHB) between January and December 2010. Participants were included in the audit if they met the above selection criteria for bariatric surgery and had completed baseline questionnaires prior to bariatric surgery at any time forward from December 2008 to December 2010. Participants completed the baseline questionnaire at a pre-operative information seminar and returned this at their first pre-operative clinic visit. Following a bariatric intervention patient's repeated the SF-36 questionnaire post-procedure at their 6-month follow-up clinic appointment through to the end of the audit period. The Northern Regional Ethics Committee X approved the audit (NTX/10/01/EXP/001). The SF-36 is a widely used generic instrument to measure HRQoL. The SF-36 contains 36 questions, 35 of which measure perceived health using a 0-100 scale across eight domains - physical functioning, role limitations due to physical functioning, bodily pain, general health, vitality, social functioning, role limitation due to emotional problems and mental health and the last item measures health transition, which is not reported here.8 Higher scores reflect better perceived health, with 100 being the best possible score for a domain. The eight domains can also be summarised into two component summary scores, namely the physical and mental component summary scores (PCS and MCS respectively).9 Both scores were normalised to have a mean of 50 and a standard deviation of 10. Scores below 50 represent scores below the population mean. As the standard deviation is 10, each point below 50 represents 0.1 of a standard deviation. Statistical analyses—Student's paired t-test was used to examine differences between matched pairs, with statistical significance set at 5%. Missing data were handled as per standard procedures.10 Briefly, where greater than 50% of items in a multi-question domain (e.g. role physical and vitality) were answered, a person specific estimate or average score of completed questions within the same domain was used. To assess the size of any changes between baseline and post-procedure scores at 6 months, standardised response means (SRM) were calculated. SRMs are the change in outcome divided by the standard deviation of the change and thus remove the noise of variance of the change leaving only the signal. Cohen's criteria for effect sizes were utilised when assessing the size of the SRMs.11 SRMs of greater than 0.8 were considered large, 0.5 to 0.79 were considered moderate, 0.2 to 0.49 were considered small and SRMs less than 0.2 were considered trivial.12 All analyses were carried out in SPSS (version 18) software. Results Forty patients completed baseline SF-36 questionnaires prior to bariatric surgery. Twelve patients had either not received bariatric surgery or had not completed the 6 month follow up by the end of the audit period. Twenty-eight patients underwent bariatric surgery and completed SF-36 questionnaires at 6 months post-procedure during the audit period. Twenty-three patients underwent laparoscopic Roux-en-Y gastric bypass and five underwent laparoscopic sleeve gastrectomy. These patients were predominantly New Zealand European, female, and class III obese (Table 1). Fifteen patients were diabetic. Table 1. Patient characteristics and comorbidities at baseline and 6 months after the bariatric procedure Variables Baseline 6 months Number (%) Number (%) Age (mean, SD) 42.8 (9.9) Female 22 (78.6) Ethnicity NZ European/Other Maori Pacific Asian 19 (67.8) 4 (14.3) 3 (10.7) 2 (7.1) Weight (kg, mean, SD) 131.2 (19.6) 94.4 (13.6) BMI (kg/m2, mean, SD) 45.3 (6.1) 32.6 (4.1) Obesity class Overweight Class I (BMI 30-34.99) Class II (BMI 35-39.99) Class III (BMI ≥40) - 1 (3.6) 4 (14.3) 23 (82.1) 12 (42.9) 6 (21.4) 2 (7.1) 8 (28.6) Type 2 diabetes mellitus Diet controlled - 1 (3.6) Oral hypoglycaemics 12 (42.9) 2 (7.1) Insulin 3 (10.7) 1 (3.6) The mean SF-36 domain and component summary scores are provided in Table 2. The baseline PCS and MCS reflect scores well below the population norms. There was significant improvement in all SF-36 scores across all domains at 6 months. The mean differences ranged from a low of 15.3 on the mental health domain to a high of 45.8 in the general health domain. The change in the PCS would indicate that the patients moved from scores 1.5 standard deviations below the population mean prior to surgery to the population mean 6 months after surgery. The change in the MCS was not as dramatic, but still represents a shift of one standard deviation to slightly better than the population mean 6 months after the surgery. Table 2. Difference between SF-36 domain scores at baseline and 6 months after bariatric procedure (n=28) Domain Baseline 6 months Mean difference (95% CI) P value Mean Mean Physical functioning 53.1 86.1 33.0 (21.4-44.6) <0.001 Role physical 45.5 81.3 35.7 (15.4-56.1) 0.001 Bodily pain 45.5 77.1 31.6 (20.0-43.3) <0.001 General health 41.5 84.6 45.8 (37.0-54.6) <0.001 Vitality 38.8 72.9 34.1 (24.8-43.4) <0.001 Social functioning 58.9 87.1 28.1 (17.0-39.2) <0.001 Role emotional 67.9 83.3 17.3 (2.5-32.1) 0.024 Mental health 67.4 82.7 15.3 (7.3-23.2) 0.001 PCS 36.0 50.1 15.3 (10.3-20.2) <0.001 MCS 42.5 52.8 12.9 (8.2-17.7) <0.001 PCS = Physical Component Summary score, MCS = Mental Component Summary score. The SRMs for the mean differences were between 0.5 for the role emotional domain to 2.2 for the general health domain (Table 3). Although the change in the role physical, role emotional and mental health domains is a moderate sized change, the change in the remaining five domains is large. As would be expected from the large changes in some of the constituent scores, the changes in the PCS and MCS scores could also be considered large. Table 3. Standardised response means to measure size of change SF-36 Health Related Quality of Life Domain Mean difference SE SRM Effect Physical functioning 33.0 5.7 1.1 Large Role physical 35.7 9.9 0.7 Moderate Bodily pain 31.6

Summary

Abstract

Aim

To explore the impact of bariatric surgery on health-related quality of life (HRQoL).

Method

An audit of patients referred for bariatric procedures. Patients completed Short Form-36 questionnaires at their first pre-operative clinic and at their 6-month follow up appointment after surgery. SF-36 scores were compared with standard parametric tests.

Results

40 patients completed baseline SF-36 questionnaires and underwent bariatric surgery, 28 were surveyed again 6 months post-procedure during the audit period between December 2008 and December 2010. Twenty-three patients underwent laparoscopic Roux-en-Y gastric bypass and five underwent laparoscopic sleeve gastrectomy. The patients were predominantly New Zealand European, female, with a body mass index greater than 40 kg/m2. Significant improvements in health-related quality of life were observed. The physical and mental component summary scores were initially well below the population norms, but increased to the norm 6 months after surgery.

Conclusion

The HRQoL of morbidly obese patients significantly improves after bariatric surgery. Services including the SF-36 in their measurement armamentarium can demonstrate the Services impact on patient- perceived outcomes in addition to clinically-focused outcomes.

Author Information

Briar McLeod, Parenteral Nutrition Clinical Nurse Specialist, Auckland District Health Board; Grant Beban, Consultant Surgeon, Auckland District Health Board; Jill Sanderson, Upper Gastrointestinal Clinical Nurse Specialist, Auckland District Health Board; Ann McKillop, Senior Lecturer, School of Nursing, University of Auckland; Andrew Jull, Associate Professor, School of Nursing and Senior Research Fellow, Clinical Trials Research Unit, School of Population Health, University of Auckland

Acknowledgements

Correspondence

Briar McLeod, PN Clinical Nurse Specialist, Auckland District Health Board, Private Bag 92024, Auckland, New Zealand. Fax: +64 (0)9 3754334

Correspondence Email

briarmcl@adhb.govt.nz

Competing Interests

None known.

Ministry of Health. Body Size Technical Report: Measurements and classifications in the 2006/07 New Zealand Health Survey. Wellington: Ministry of Health, 2008.Ministry of Health. A portrait of health. Key results of the 2006/07 New Zealand health survey. Wellington: Ministry of Health, 2008.Ministry of Health, Clinical Trials Research Unit. Clinical Guidelines for Weight Management in New Zealand Adults. Wellington: Ministry of Health, 2009.Jull A, Lawes CMM, Eyles H, et al. Clinical guidelines for weight management in New Zealand adults, children and young people. J Prim Health Care 2011;3(1):66-71.Sjostrom L, Lindroos AK, Peltonen M, et al. Lifestyle, diabetes, and cardiovascular risk factors 10 years after bariatric surgery. N Engl J Med 2004;351(26):2683-93.He M, Stubbs R. Gastric bypass surgery for severe obesity: what can be achieved? NZ Med J 2004;117(1207):1-14.Consensus Development Conference Panel. NIH Conference Gastrointestinal surgery for severe obesity. Ann Intern Med 1991;115(12):956-61.Ware J, Snow K, Kosinski M, Gandek B. SF-36 Health Survey: manual & interpretation guide. Boston: Nimrod Press, 1993.Ware JE, Kosinki M, Keller SD. SF-36 physical and mental health summary scores: a user's manual. Boston: The Health Institute, 1994.Ware JE, Snow KK, Kosinski M, Gandek MS. SF-36 Health survey: manual and interpretation guide. Lincoln: QualityMetric Incorporated, 2000.Cohen J. Statistical power analysis for the behavioral sciences. 2nd ed. Hillsdale, New Jersey: Lawrence Erlbaum Associates Incorporated, 1988.Hays RD, Farivar SS, Liu H. Approaches and recommendations for estimating a minimally important differences for health-related quality of life measures. J Chronic Obstruct Pulmon Dis 2005;2:63-7.Ni Mhurchu C, Bennett D, Lin R, et al. Obesity and health-related quality of life: results from a weight loss trial. NZ Med J 2004;117(1207):1-9.van Nunen AM, Wouters EJ, Vingerhoets AJ, et al. The health-related quality of life of obese persons seeking or not seeking surgical or non-surgical treatment: a meta-analysis. Obes Surg 2007;17:1357-66.Rea JD, Yarbrough DE, Leeth RR, et al. Influence of complications and extent of weight loss on quality of life after laparoscopic Roux-en-Y gastric bypass. Surg Endosc 2007;21(7):1095-100.van Hout GC, Fortuin FA, Pelle AJ, et al. Health-related quality of life following vertical banded gastroplasty. Surg Endosc 2009;23(3):550-6.Nguyen NT, Slone JA, Nguyen XT, et al. A prospective randomised trial of laparoscopic gastric bypass versus laparoscopic adjustable gastric banding for the treatment of morbid obesity. Ann Surg 2009;250(4):631-41.Kolotkin RL, Crosby RD, Gress RE, et al. Two-year changes in health-related quality of life in gastric bypass patients compared with severely obese controls. Surg Obes Relat Dis 2009;5(2):250-6.Dixon JB, Dixon ME, O'Brien PE. Quality of life after lap-band placement: influence of time, weight loss, and comorbidities. Obes Res 2001;9(11):713--21.Karlsson J, Taft C, Ryden A, et al. Ten-year trends in health-related quality of life after surgical and conventional treatment for severe obesity: the SOS intervention study. Int J Obes 2007;31(8):1248-61.Husted JA, Cook RJ, Farewell VT, Galdman DD. Methods for assessing responsiveness: a critical review and recommendations J Clin Epidemiol 2000;53(5):459-68.

For the PDF of this article,
contact nzmj@nzma.org.nz

View Article PDF

Obesity is a major problem in New Zealand with the direct-care costs estimated at $460 million.1 Although the growth of obesity may be slowing, its prevalence remains high (26.5%) and 9.1% of the population are morbidly obese.2 Obesity is associated with increased risk of mortality from cardiovascular disease and some cancers, a higher incidence of numerous conditions including diabetes, hypertension, joint disorders and obstructive sleep apnoea.3Bariatric surgery is a safe and effective way of managing morbid obesity for selected individuals and a recommended approach in the New Zealand guidelines for weight management.3,4 Weight associated comorbidities frequently resolve after bariatric procedures.5Bariatric surgery has been offered by the Auckland District Health Board (ADHB) since 2008. Mainly Roux-en-Y gastric bypass or sleeve gastrectomies are carried out. The effect of bariatric surgery on clinical outcomes has been investigated in New Zealand,6 but no estimate of the effect of the surgery on patient-oriented outcomes has been reported in New Zealand.The ADHB Bariatric Service has been routinely collecting self-reported perceived health using the SF-36 and this data offered the opportunity to measure the impact of bariatric surgery on the patient's perception of their health-related quality of life (HRQoL).Methods Background—The ADHB Bariatric Service has selection criteria for bariatric surgery aligned with that proposed by the National Institute of Health.7 Patients must be aged between 18 and 60 years, have a body mass index of greater than 40 kg/m2, or greater than 35 kg/m2 with obesity-related comorbidity, and have been obese for more than five years with failed non-surgical attempts at weight loss. The Service is not available if a patient's weight is greater than 170 kg or their body mass index (BMI) of is greater than 55 kg/m2 or if they are considered a high operative risk due to end stage disease. Participants and study design—An audit was carried out at Auckland District Health Board (ADHB) between January and December 2010. Participants were included in the audit if they met the above selection criteria for bariatric surgery and had completed baseline questionnaires prior to bariatric surgery at any time forward from December 2008 to December 2010. Participants completed the baseline questionnaire at a pre-operative information seminar and returned this at their first pre-operative clinic visit. Following a bariatric intervention patient's repeated the SF-36 questionnaire post-procedure at their 6-month follow-up clinic appointment through to the end of the audit period. The Northern Regional Ethics Committee X approved the audit (NTX/10/01/EXP/001). The SF-36 is a widely used generic instrument to measure HRQoL. The SF-36 contains 36 questions, 35 of which measure perceived health using a 0-100 scale across eight domains - physical functioning, role limitations due to physical functioning, bodily pain, general health, vitality, social functioning, role limitation due to emotional problems and mental health and the last item measures health transition, which is not reported here.8 Higher scores reflect better perceived health, with 100 being the best possible score for a domain. The eight domains can also be summarised into two component summary scores, namely the physical and mental component summary scores (PCS and MCS respectively).9 Both scores were normalised to have a mean of 50 and a standard deviation of 10. Scores below 50 represent scores below the population mean. As the standard deviation is 10, each point below 50 represents 0.1 of a standard deviation. Statistical analyses—Student's paired t-test was used to examine differences between matched pairs, with statistical significance set at 5%. Missing data were handled as per standard procedures.10 Briefly, where greater than 50% of items in a multi-question domain (e.g. role physical and vitality) were answered, a person specific estimate or average score of completed questions within the same domain was used. To assess the size of any changes between baseline and post-procedure scores at 6 months, standardised response means (SRM) were calculated. SRMs are the change in outcome divided by the standard deviation of the change and thus remove the noise of variance of the change leaving only the signal. Cohen's criteria for effect sizes were utilised when assessing the size of the SRMs.11 SRMs of greater than 0.8 were considered large, 0.5 to 0.79 were considered moderate, 0.2 to 0.49 were considered small and SRMs less than 0.2 were considered trivial.12 All analyses were carried out in SPSS (version 18) software. Results Forty patients completed baseline SF-36 questionnaires prior to bariatric surgery. Twelve patients had either not received bariatric surgery or had not completed the 6 month follow up by the end of the audit period. Twenty-eight patients underwent bariatric surgery and completed SF-36 questionnaires at 6 months post-procedure during the audit period. Twenty-three patients underwent laparoscopic Roux-en-Y gastric bypass and five underwent laparoscopic sleeve gastrectomy. These patients were predominantly New Zealand European, female, and class III obese (Table 1). Fifteen patients were diabetic. Table 1. Patient characteristics and comorbidities at baseline and 6 months after the bariatric procedure Variables Baseline 6 months Number (%) Number (%) Age (mean, SD) 42.8 (9.9) Female 22 (78.6) Ethnicity NZ European/Other Maori Pacific Asian 19 (67.8) 4 (14.3) 3 (10.7) 2 (7.1) Weight (kg, mean, SD) 131.2 (19.6) 94.4 (13.6) BMI (kg/m2, mean, SD) 45.3 (6.1) 32.6 (4.1) Obesity class Overweight Class I (BMI 30-34.99) Class II (BMI 35-39.99) Class III (BMI ≥40) - 1 (3.6) 4 (14.3) 23 (82.1) 12 (42.9) 6 (21.4) 2 (7.1) 8 (28.6) Type 2 diabetes mellitus Diet controlled - 1 (3.6) Oral hypoglycaemics 12 (42.9) 2 (7.1) Insulin 3 (10.7) 1 (3.6) The mean SF-36 domain and component summary scores are provided in Table 2. The baseline PCS and MCS reflect scores well below the population norms. There was significant improvement in all SF-36 scores across all domains at 6 months. The mean differences ranged from a low of 15.3 on the mental health domain to a high of 45.8 in the general health domain. The change in the PCS would indicate that the patients moved from scores 1.5 standard deviations below the population mean prior to surgery to the population mean 6 months after surgery. The change in the MCS was not as dramatic, but still represents a shift of one standard deviation to slightly better than the population mean 6 months after the surgery. Table 2. Difference between SF-36 domain scores at baseline and 6 months after bariatric procedure (n=28) Domain Baseline 6 months Mean difference (95% CI) P value Mean Mean Physical functioning 53.1 86.1 33.0 (21.4-44.6) <0.001 Role physical 45.5 81.3 35.7 (15.4-56.1) 0.001 Bodily pain 45.5 77.1 31.6 (20.0-43.3) <0.001 General health 41.5 84.6 45.8 (37.0-54.6) <0.001 Vitality 38.8 72.9 34.1 (24.8-43.4) <0.001 Social functioning 58.9 87.1 28.1 (17.0-39.2) <0.001 Role emotional 67.9 83.3 17.3 (2.5-32.1) 0.024 Mental health 67.4 82.7 15.3 (7.3-23.2) 0.001 PCS 36.0 50.1 15.3 (10.3-20.2) <0.001 MCS 42.5 52.8 12.9 (8.2-17.7) <0.001 PCS = Physical Component Summary score, MCS = Mental Component Summary score. The SRMs for the mean differences were between 0.5 for the role emotional domain to 2.2 for the general health domain (Table 3). Although the change in the role physical, role emotional and mental health domains is a moderate sized change, the change in the remaining five domains is large. As would be expected from the large changes in some of the constituent scores, the changes in the PCS and MCS scores could also be considered large. Table 3. Standardised response means to measure size of change SF-36 Health Related Quality of Life Domain Mean difference SE SRM Effect Physical functioning 33.0 5.7 1.1 Large Role physical 35.7 9.9 0.7 Moderate Bodily pain 31.6

Summary

Abstract

Aim

To explore the impact of bariatric surgery on health-related quality of life (HRQoL).

Method

An audit of patients referred for bariatric procedures. Patients completed Short Form-36 questionnaires at their first pre-operative clinic and at their 6-month follow up appointment after surgery. SF-36 scores were compared with standard parametric tests.

Results

40 patients completed baseline SF-36 questionnaires and underwent bariatric surgery, 28 were surveyed again 6 months post-procedure during the audit period between December 2008 and December 2010. Twenty-three patients underwent laparoscopic Roux-en-Y gastric bypass and five underwent laparoscopic sleeve gastrectomy. The patients were predominantly New Zealand European, female, with a body mass index greater than 40 kg/m2. Significant improvements in health-related quality of life were observed. The physical and mental component summary scores were initially well below the population norms, but increased to the norm 6 months after surgery.

Conclusion

The HRQoL of morbidly obese patients significantly improves after bariatric surgery. Services including the SF-36 in their measurement armamentarium can demonstrate the Services impact on patient- perceived outcomes in addition to clinically-focused outcomes.

Author Information

Briar McLeod, Parenteral Nutrition Clinical Nurse Specialist, Auckland District Health Board; Grant Beban, Consultant Surgeon, Auckland District Health Board; Jill Sanderson, Upper Gastrointestinal Clinical Nurse Specialist, Auckland District Health Board; Ann McKillop, Senior Lecturer, School of Nursing, University of Auckland; Andrew Jull, Associate Professor, School of Nursing and Senior Research Fellow, Clinical Trials Research Unit, School of Population Health, University of Auckland

Acknowledgements

Correspondence

Briar McLeod, PN Clinical Nurse Specialist, Auckland District Health Board, Private Bag 92024, Auckland, New Zealand. Fax: +64 (0)9 3754334

Correspondence Email

briarmcl@adhb.govt.nz

Competing Interests

None known.

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