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Assault resulting in injury is a significant public health problem in New Zealand. The most recently available national data indicates assaultive deaths account for 3.5% of all injury deaths and 3.4% of hospital discharges.1,2Assault attracts considerable public and media attention, and is one of six priority areas for the New Zealand Injury Prevention Strategy (NZIPS) 3. A key focus of NZIPS is to cenhance the infrastructure that supports injury prevention activity to improve injury prevention performanced.A recent review of that strategy reported that between 2003 and 2008 there was a 50% increase in the age standardised rates of serious non-fatal assaultive injury 4. However, no further insight was provided concerning the risk factors for, or characteristics of, assaultive injury. Nor has then been any other recent published NZ research that might provide further insight into epidemiological trends of these more serious events.Accordingly we sought to describe the: (1) Distribution of serious non-fatal assault injury for the period 2000-2009 by sociodemographic characteristics, location of incidents, methods used to inflict injury, alcohol involvement, and nature of injury; and (2) Trends in serious assault injury by age, gender, and method. Methods We used the same methods for defining a serious non-fatal assault case as that are used in the NZIPS chartbooks.5 Briefly, this consisted of identifying all cases in the National Minimum Data Set of hospital discharges (NMDS) with: An International Classifications of Diseases and Related Health Problems, version 10, Australian Modification (ICD-10-AM) injury related principal diagnosis (ICD-10-AM diagnosis code S00-T78), (b) where the first cause of injury was recorded as assault (ICD-10-AM external cause codes X85-Y09), Which resulted in injuries which were high-threat to life (6% or more chance of dying), The victim was discharged in the period 2000-2009. Readmissions for follow-up treatment were excluded. Public hospitals provide 99.5% of inpatient treatment of injury in the acute phase. For the purposes of providing a measure of treatment resource impact we estimated the cumulative bed days stay associated with each case. This measure is the sum of the days stayed over the first visit and any subsequent readmission related to the incident. All records which meet the above criteria were searched for ICD-10-AM diagnosis and external cause codes indicative of alcohol involvement using the approach adopted by a US study of non-fatal suicide acts which resulted in hospitalisation.6 Records with ICD-10-AM codes indicating alcohol intoxication [Mental and behavioural disorders due to use of alcohol (F10): acute intoxication (F10.0), harmful use (F10.1) dependence syndrome ( F10.2) residual and late onset psychotic disorder (F10.7), psychotic disorder(F10.5)] were identified. Additional records with external cause of injury codes indicative of accidental poisoning by and exposure to alcohol (X45), intentional poisoning by and exposure to alcohol (X65) or alcohol poisoning intent undetermined (Y15) were also flagged as alcohol involved, as were those with diagnosis codes that included problems related to lifestylealcohol use (Z72.1), and evidence of alcohol involvement as determined by blood alcohol level (Y90.0-Y90.9). Cases were only counted as being alcohol involved once, irrespective of the number of alcohol related diagnosis or external cause of injury codes recorded in the hospital record. The NMDS records self-defined ethnicity in which patients may self-report up to three ethnic groups to which they belong. For those who report multiple ethnicities, the concept of ethnicity for this investigation has been defined in line with NMDS reporting: ethnicity is prioritised with M ori ethnicity receiving the top priority, followed by Pacific Islander, Asian and finally European. Residential area deprivation levels (NZDep2006) were based on the residential address of the assault victim as recorded in the NMDS. NZDep2006 scores are derived from Statistics New Zealand census data and combine measures of income, home ownership, support, employment, qualifications, living space, communication and transport to provide a measure of the relative level of deprivation for census meshblock areas (each meshblock contains approximately 87 people in 2006 and represent the area covered by a single census enumerator). Residential areas are assigned a value on an ordinal score from 1 (least deprived) to 10 (most deprived).7 Assault victims were assigned area deprivation scores based on their residential address. Denominators for rates were obtained from the Statistics New Zealand usually resident population estimates (series 5) for June 30 of the relevant year. Series 5 estimates assume medium fertility, medium mortality and long-run annual net migration of 10,000. For the calculation of ethnic specific rates, Statistics New Zealand population estimates for the relevant ethnic group, as at June 30 of the relevant year was used as the denominator. Ethnic-specific population estimates for M ori, Pacific Island and Asian populations were only available for the period 2006 onwards. These rates were age standardised. Age standardisation was via the direct method with five year age bands from 0-4 years to 85 and 85+ years. The standard population was the New Zealand population 2006 as at June 2006. Calculation of crude rates for NZDep2006 decile categories were based on Statistics New Zealand census area unit population estimates, available for the period 2006 onwards, as at June 30 of the relevant years. Statistics New Zealand provides mapping files that allow meshblocks used in the calculation of NZDep scores to be mapped to larger geographical area units, such as census area unit population estimates. NZDep scores for larger area units are derived from the average NZDep scores of the meshblocks included. 95% confidence intervals for rates assume a Poisson distribution. Ethics approval for this investigation was obtained from the New Zealand Multi-region Ethics Committee (Reference number OTA/99/02/008). Results For the period 2000-2009 inclusive there were 8006 serious non-fatal assaults (average annualised rate of 19.56 per 100,000 per year). Overall males accounted for the bulk (76%) of the burden of assault (Table 1). Males aged 15-24 years had the highest rates of assault. This rate was approximately five times the highest age specific rate for females (25-34 year olds). Table 1. Sociodemographic characteristics of serious non-fatal assaults by gender 2000-2009 Variables Males (n=6,335) Females (n=1671) N % Rate (95%CI) N % Rate (95%CI) Age 0-14 years 15-24 years 25-34 years 35-49 years 50-64 years 65+ years 239 2409 1633 1530 416 108 3.8 38.0 25.8 24.2 6.6 1.7 5.3 (4.6-6.0) 81.6 (78.4-84.9) 61.6 (58.7-64.7) 34.6 (32.9-36.4) 12.7 (11.5-14.0) 4.9 (4.0-5.9) 156 423 463 481 98 50 9.3 25.3 27.7 28.8 5.9 3.0 3.6 (3.1-4.2) 14.7 (13.3-16.2) 16.3 (14.8-17.9) 10.2 (9.3-11.2) 2.9 (2.4-3.6) 1.8 (1.4-2.4) TOTAL 6335 100 1671 100 Ethnicity M ori Pacific Island Asian NZ European/ other 992 429 145 1563 31.7 13.7 4.6 50.0 2006-2009 77.4 (72.3-82.4) 67.8 (60.8-74.7) 14.8 (12.2-17.4) 26.0 (24.7-27.3) 380 72 31 312 47.8 9.1 3.9 39.3 2006-2009 28.0 (24.1-30.9) 11.0 (8.5-13.6) 3.2 (2.0-4.4) 4.8 (4.3-5.4) NZDep 2006 Score 1 (least deprived) 2 3 4 5 6 7 8 9 10 (most deprived) 30 227 420 502 615 633 961 898 1095 519 0.5 3.9 7.1 8.5 10.4 10.7 16.3 15.2 18.6 8.8 Crude rates 2006-2009 2.5 (1.5-3.9) 13.4 (11.1-16.1) 26.8 (23.3-30.7) 27.6 (24.1-31.6) 36.2 (32.3-40.4) 36.1 (32.1-40.5) 56.9 (51.9-62.6) 50.6 (46.2-55.4) 64.9 (59.7-70.4) 31.1 (27.4-35.0) 13 30 100 147 158 140 219 260 336 166 0.8 1.9 6.4 9.4 10.1 8.9 14.0 16.6 21.4 10.6 Crude rates 2006-2009 0.8 (0.2-1.7) 2.4 (1.5-3.7) 6.4 (4.8-8.5) 8.1 (6.2-10.3) 8.2 (6.4-10.3) 7.9 (6.1-10.0) 12.9 (10.7-15.5) 14.1 (11.8-16.6) 17.5 (15.0-20.4) 8.1 (6.4-10.2) For males there was a marked and consistent increase in rates among 15-24 year olds over time (Figure 1). The trend for females in this age group was very variable. The trend for the 25-34 year olds showed a more consistent and marked increase over time (Figure 2). Figure 1. Serious non-fatal assault, annual rates by age group, males only Figure 2. Serious non-fatal assault, annual rates by age group, females only M ori accounted for almost half (48%) of female and one third (32%) of male serious non-fatal assaults (Table 1). Pacific Island people also figured prominently among the male statistics having a rate only slightly lower than M ori males. Between 2006 and 2009 the rates of serious non-fatal assault increased for M ori from 43.6/100,000-62.6/100,000, for Pacific Islanders from 37.3/100,000 to 38.6/100,000, for Asians from 7.7/100,000 to 9.1/100,000 and for New Zealand European/Other from 13.3/100,000 to 15.8/100,000. For both males and females the rates for NZDep groups 7, 8 and 9 were 17-26 times higher than that for the least deprived group for females and 32-39 times higher than the least deprived group for the males. Overall, the home (26%), and the street/highway (18%) were the most common locations of incidents (Table 2). There was a difference in the location of the injury scene by gender, for female victims, 56% of assaultive injury events occurred in the home, in comparison with 20% for male victims; while 24% of assaultive injuries for males occurred in the street/highway compared with 10% for females. There was a high proportion of victims for which no information was recorded about the location of the injury event35.5% of male cases and 24.5% of female cases (Table 2). Table 2. Circumstances of serious non-fatal assaults by gender 2000-2009 Variables Males (n=6335) Females (n=1671) N % N % Injury scene Home Residential institution School/admin Sports/athletics area Street/highway Trade/service area Industrial area Farm Other specified Unspecified 1188 162 88 57 1397 583 20 7 322 2108 20.0 2.7 1.5 1.0 23.6 9.8 0.3 0.1 5.4 35.5 855 15 20 1 156 58 3 0 50 375 55.8 1.0 1.3 0.1 10.2 3.8 0.2 0.0 3.3 24.5 Method Hanging Firearms Smoke Vapours Sharp object Blunt object Bodily force Neglect All other* 14 32 18 13 953 1284 2879 125 1017 0.2 0.5 0.3 0.2 15.0 20.3 45.5 2.0 16.1 41 5 8 12 118 214 820 213 240 2.5 0.3 0.5 0.7 7.0 12.8

Summary

Abstract

Aim

To describe the distribution of, and trends in, the characteristics of serious nonfatal assault injury for the period 2000-2009.

Method

Serious non-fatal hospitalised assault injury for the 2000-2009 period were identified and described by: sociodemographic characteristics, location of incidents, methods used to inflict injury, alcohol involvement, and nature of injury. Trends in assault by age, gender, and method were examined.

Results

Males, 15-24 year olds, Maori, Pacific Islanders, and those from deprived neighbourhoods had markedly elevated assault rates. Assault by bodily force and head injuries predominated with the former being the major category of assault that increased the most over time

Conclusion

There is a disturbing level of serious assault in New Zealand and the situation is getting worse. We need to review current efforts to prevent these incidents.

Author Information

John Langley, Emeritus Professor; Pauline Gulliver, Senior Research Fellow; Injury Prevention Research Unit (http://www.otago.ac.nz/ipru), Dept of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin

Acknowledgements

The authors thank Colin Cryer, Gabrielle Davie and Kypros Kypri for helpful comments on earlier versions of this paper.

Correspondence

J Langley, Injury Prevention Research Unit, Dept of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, PO Box 56, Dunedin 9054, New Zealand. Fax: +64 (0)3 4798337

Correspondence Email

John.langley@otago.ac.nz

Competing Interests

None known.

Ministry of Health. Mortality Data Collection. Wellington 2009.Ministry of Health. National Minimum Data Set. Wellington, 2010.Dyson R. New Zealand Injury Prevention Strategy. Wellington: New Zealand Government, 2003:1-28.New Zealand Injury Prevention Secreteriat. New Zealand Injury Prevention Strategy, Five-year Evaluation- Final Report May 2010. Wellington, 2010.Cryer C, Langley J, Stephenson S. Developing Valid Injury Outcome Indicators: A report for the New Zealand Injury Prevention Strategy. Dunedin: University of Otago, 2004:1-141.Miller T, Teti L, Lawrence B, Weiss H. Alcohol Involvement in Hospital-Admitted Nonfatal Suicide Acts. Suicide and Life-Threatening Behavior 2010;40:492-9.Salmond C, Crampton P, Atkinson J. NZDep2006 Index of Deprivation. Wellington, 2007.Ministry of Justice. Knife Possession: Briefing paper for Minister of Justice. Wellington, 2010.Cherpitel C, Borges G, Giesbrechtl N, et al. Alcohol and Injuries; Emergency Department Studies in an International Perspective. Geneva: World Health Organisation, 2009.Connor J, Kypri K, Bell L. Alcohol involvement in aggression between intimate partners in New Zealand: a national cross-sectional study. BMJ Open 2011(doi:10.1136/bmjopen-2011-000065).Chalmers DJ, Fanslow JL, Langley JD. Injury from assault in New Zealand: an increasing public health problem. Aust J Public Health 1995;19(2):149-54.Gawryszewski VP, da Silva MMA, Malta DC, et al. Violence-related injury in emergency departments in Brazil. Rev Panam Salud Publica 2008;24(6):400-8.Sivarajasingam V, Shepherd J, Mathews K, Jones S. Violence-related injury data in England and Wales. British Journal of Criminology 2003;43:223-27.Rand M. Violence-related injuries treated in hospital emergency departments. Washington DC, 1997.Porteous D. Violence now in third generation: Judge. Otago Daily Times 2011.Shepherd J, Sivarajasingam V. Injury research explains conflicting violence trends. Injury Prevention 2005;11(6):324-5.Langley J. Emergency department data suffer similar threats to validity as police data Injury Prevention 2006;12:208.Cryer C, Langley JD, Stephenson SCR, et al. Measure for measure: the quest for valid indicators of non-fatal injury incidence. Public Health 2002;116(5):257-62.Gulliver P, Cryer C, Davie G. Investigation of provisional status of the NZIPS serious non-fatal assault and self harm indicators. Dunedin, 2009.

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Assault resulting in injury is a significant public health problem in New Zealand. The most recently available national data indicates assaultive deaths account for 3.5% of all injury deaths and 3.4% of hospital discharges.1,2Assault attracts considerable public and media attention, and is one of six priority areas for the New Zealand Injury Prevention Strategy (NZIPS) 3. A key focus of NZIPS is to cenhance the infrastructure that supports injury prevention activity to improve injury prevention performanced.A recent review of that strategy reported that between 2003 and 2008 there was a 50% increase in the age standardised rates of serious non-fatal assaultive injury 4. However, no further insight was provided concerning the risk factors for, or characteristics of, assaultive injury. Nor has then been any other recent published NZ research that might provide further insight into epidemiological trends of these more serious events.Accordingly we sought to describe the: (1) Distribution of serious non-fatal assault injury for the period 2000-2009 by sociodemographic characteristics, location of incidents, methods used to inflict injury, alcohol involvement, and nature of injury; and (2) Trends in serious assault injury by age, gender, and method. Methods We used the same methods for defining a serious non-fatal assault case as that are used in the NZIPS chartbooks.5 Briefly, this consisted of identifying all cases in the National Minimum Data Set of hospital discharges (NMDS) with: An International Classifications of Diseases and Related Health Problems, version 10, Australian Modification (ICD-10-AM) injury related principal diagnosis (ICD-10-AM diagnosis code S00-T78), (b) where the first cause of injury was recorded as assault (ICD-10-AM external cause codes X85-Y09), Which resulted in injuries which were high-threat to life (6% or more chance of dying), The victim was discharged in the period 2000-2009. Readmissions for follow-up treatment were excluded. Public hospitals provide 99.5% of inpatient treatment of injury in the acute phase. For the purposes of providing a measure of treatment resource impact we estimated the cumulative bed days stay associated with each case. This measure is the sum of the days stayed over the first visit and any subsequent readmission related to the incident. All records which meet the above criteria were searched for ICD-10-AM diagnosis and external cause codes indicative of alcohol involvement using the approach adopted by a US study of non-fatal suicide acts which resulted in hospitalisation.6 Records with ICD-10-AM codes indicating alcohol intoxication [Mental and behavioural disorders due to use of alcohol (F10): acute intoxication (F10.0), harmful use (F10.1) dependence syndrome ( F10.2) residual and late onset psychotic disorder (F10.7), psychotic disorder(F10.5)] were identified. Additional records with external cause of injury codes indicative of accidental poisoning by and exposure to alcohol (X45), intentional poisoning by and exposure to alcohol (X65) or alcohol poisoning intent undetermined (Y15) were also flagged as alcohol involved, as were those with diagnosis codes that included problems related to lifestylealcohol use (Z72.1), and evidence of alcohol involvement as determined by blood alcohol level (Y90.0-Y90.9). Cases were only counted as being alcohol involved once, irrespective of the number of alcohol related diagnosis or external cause of injury codes recorded in the hospital record. The NMDS records self-defined ethnicity in which patients may self-report up to three ethnic groups to which they belong. For those who report multiple ethnicities, the concept of ethnicity for this investigation has been defined in line with NMDS reporting: ethnicity is prioritised with M ori ethnicity receiving the top priority, followed by Pacific Islander, Asian and finally European. Residential area deprivation levels (NZDep2006) were based on the residential address of the assault victim as recorded in the NMDS. NZDep2006 scores are derived from Statistics New Zealand census data and combine measures of income, home ownership, support, employment, qualifications, living space, communication and transport to provide a measure of the relative level of deprivation for census meshblock areas (each meshblock contains approximately 87 people in 2006 and represent the area covered by a single census enumerator). Residential areas are assigned a value on an ordinal score from 1 (least deprived) to 10 (most deprived).7 Assault victims were assigned area deprivation scores based on their residential address. Denominators for rates were obtained from the Statistics New Zealand usually resident population estimates (series 5) for June 30 of the relevant year. Series 5 estimates assume medium fertility, medium mortality and long-run annual net migration of 10,000. For the calculation of ethnic specific rates, Statistics New Zealand population estimates for the relevant ethnic group, as at June 30 of the relevant year was used as the denominator. Ethnic-specific population estimates for M ori, Pacific Island and Asian populations were only available for the period 2006 onwards. These rates were age standardised. Age standardisation was via the direct method with five year age bands from 0-4 years to 85 and 85+ years. The standard population was the New Zealand population 2006 as at June 2006. Calculation of crude rates for NZDep2006 decile categories were based on Statistics New Zealand census area unit population estimates, available for the period 2006 onwards, as at June 30 of the relevant years. Statistics New Zealand provides mapping files that allow meshblocks used in the calculation of NZDep scores to be mapped to larger geographical area units, such as census area unit population estimates. NZDep scores for larger area units are derived from the average NZDep scores of the meshblocks included. 95% confidence intervals for rates assume a Poisson distribution. Ethics approval for this investigation was obtained from the New Zealand Multi-region Ethics Committee (Reference number OTA/99/02/008). Results For the period 2000-2009 inclusive there were 8006 serious non-fatal assaults (average annualised rate of 19.56 per 100,000 per year). Overall males accounted for the bulk (76%) of the burden of assault (Table 1). Males aged 15-24 years had the highest rates of assault. This rate was approximately five times the highest age specific rate for females (25-34 year olds). Table 1. Sociodemographic characteristics of serious non-fatal assaults by gender 2000-2009 Variables Males (n=6,335) Females (n=1671) N % Rate (95%CI) N % Rate (95%CI) Age 0-14 years 15-24 years 25-34 years 35-49 years 50-64 years 65+ years 239 2409 1633 1530 416 108 3.8 38.0 25.8 24.2 6.6 1.7 5.3 (4.6-6.0) 81.6 (78.4-84.9) 61.6 (58.7-64.7) 34.6 (32.9-36.4) 12.7 (11.5-14.0) 4.9 (4.0-5.9) 156 423 463 481 98 50 9.3 25.3 27.7 28.8 5.9 3.0 3.6 (3.1-4.2) 14.7 (13.3-16.2) 16.3 (14.8-17.9) 10.2 (9.3-11.2) 2.9 (2.4-3.6) 1.8 (1.4-2.4) TOTAL 6335 100 1671 100 Ethnicity M ori Pacific Island Asian NZ European/ other 992 429 145 1563 31.7 13.7 4.6 50.0 2006-2009 77.4 (72.3-82.4) 67.8 (60.8-74.7) 14.8 (12.2-17.4) 26.0 (24.7-27.3) 380 72 31 312 47.8 9.1 3.9 39.3 2006-2009 28.0 (24.1-30.9) 11.0 (8.5-13.6) 3.2 (2.0-4.4) 4.8 (4.3-5.4) NZDep 2006 Score 1 (least deprived) 2 3 4 5 6 7 8 9 10 (most deprived) 30 227 420 502 615 633 961 898 1095 519 0.5 3.9 7.1 8.5 10.4 10.7 16.3 15.2 18.6 8.8 Crude rates 2006-2009 2.5 (1.5-3.9) 13.4 (11.1-16.1) 26.8 (23.3-30.7) 27.6 (24.1-31.6) 36.2 (32.3-40.4) 36.1 (32.1-40.5) 56.9 (51.9-62.6) 50.6 (46.2-55.4) 64.9 (59.7-70.4) 31.1 (27.4-35.0) 13 30 100 147 158 140 219 260 336 166 0.8 1.9 6.4 9.4 10.1 8.9 14.0 16.6 21.4 10.6 Crude rates 2006-2009 0.8 (0.2-1.7) 2.4 (1.5-3.7) 6.4 (4.8-8.5) 8.1 (6.2-10.3) 8.2 (6.4-10.3) 7.9 (6.1-10.0) 12.9 (10.7-15.5) 14.1 (11.8-16.6) 17.5 (15.0-20.4) 8.1 (6.4-10.2) For males there was a marked and consistent increase in rates among 15-24 year olds over time (Figure 1). The trend for females in this age group was very variable. The trend for the 25-34 year olds showed a more consistent and marked increase over time (Figure 2). Figure 1. Serious non-fatal assault, annual rates by age group, males only Figure 2. Serious non-fatal assault, annual rates by age group, females only M ori accounted for almost half (48%) of female and one third (32%) of male serious non-fatal assaults (Table 1). Pacific Island people also figured prominently among the male statistics having a rate only slightly lower than M ori males. Between 2006 and 2009 the rates of serious non-fatal assault increased for M ori from 43.6/100,000-62.6/100,000, for Pacific Islanders from 37.3/100,000 to 38.6/100,000, for Asians from 7.7/100,000 to 9.1/100,000 and for New Zealand European/Other from 13.3/100,000 to 15.8/100,000. For both males and females the rates for NZDep groups 7, 8 and 9 were 17-26 times higher than that for the least deprived group for females and 32-39 times higher than the least deprived group for the males. Overall, the home (26%), and the street/highway (18%) were the most common locations of incidents (Table 2). There was a difference in the location of the injury scene by gender, for female victims, 56% of assaultive injury events occurred in the home, in comparison with 20% for male victims; while 24% of assaultive injuries for males occurred in the street/highway compared with 10% for females. There was a high proportion of victims for which no information was recorded about the location of the injury event35.5% of male cases and 24.5% of female cases (Table 2). Table 2. Circumstances of serious non-fatal assaults by gender 2000-2009 Variables Males (n=6335) Females (n=1671) N % N % Injury scene Home Residential institution School/admin Sports/athletics area Street/highway Trade/service area Industrial area Farm Other specified Unspecified 1188 162 88 57 1397 583 20 7 322 2108 20.0 2.7 1.5 1.0 23.6 9.8 0.3 0.1 5.4 35.5 855 15 20 1 156 58 3 0 50 375 55.8 1.0 1.3 0.1 10.2 3.8 0.2 0.0 3.3 24.5 Method Hanging Firearms Smoke Vapours Sharp object Blunt object Bodily force Neglect All other* 14 32 18 13 953 1284 2879 125 1017 0.2 0.5 0.3 0.2 15.0 20.3 45.5 2.0 16.1 41 5 8 12 118 214 820 213 240 2.5 0.3 0.5 0.7 7.0 12.8

Summary

Abstract

Aim

To describe the distribution of, and trends in, the characteristics of serious nonfatal assault injury for the period 2000-2009.

Method

Serious non-fatal hospitalised assault injury for the 2000-2009 period were identified and described by: sociodemographic characteristics, location of incidents, methods used to inflict injury, alcohol involvement, and nature of injury. Trends in assault by age, gender, and method were examined.

Results

Males, 15-24 year olds, Maori, Pacific Islanders, and those from deprived neighbourhoods had markedly elevated assault rates. Assault by bodily force and head injuries predominated with the former being the major category of assault that increased the most over time

Conclusion

There is a disturbing level of serious assault in New Zealand and the situation is getting worse. We need to review current efforts to prevent these incidents.

Author Information

John Langley, Emeritus Professor; Pauline Gulliver, Senior Research Fellow; Injury Prevention Research Unit (http://www.otago.ac.nz/ipru), Dept of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin

Acknowledgements

The authors thank Colin Cryer, Gabrielle Davie and Kypros Kypri for helpful comments on earlier versions of this paper.

Correspondence

J Langley, Injury Prevention Research Unit, Dept of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, PO Box 56, Dunedin 9054, New Zealand. Fax: +64 (0)3 4798337

Correspondence Email

John.langley@otago.ac.nz

Competing Interests

None known.

Ministry of Health. Mortality Data Collection. Wellington 2009.Ministry of Health. National Minimum Data Set. Wellington, 2010.Dyson R. New Zealand Injury Prevention Strategy. Wellington: New Zealand Government, 2003:1-28.New Zealand Injury Prevention Secreteriat. New Zealand Injury Prevention Strategy, Five-year Evaluation- Final Report May 2010. Wellington, 2010.Cryer C, Langley J, Stephenson S. Developing Valid Injury Outcome Indicators: A report for the New Zealand Injury Prevention Strategy. Dunedin: University of Otago, 2004:1-141.Miller T, Teti L, Lawrence B, Weiss H. Alcohol Involvement in Hospital-Admitted Nonfatal Suicide Acts. Suicide and Life-Threatening Behavior 2010;40:492-9.Salmond C, Crampton P, Atkinson J. NZDep2006 Index of Deprivation. Wellington, 2007.Ministry of Justice. Knife Possession: Briefing paper for Minister of Justice. Wellington, 2010.Cherpitel C, Borges G, Giesbrechtl N, et al. Alcohol and Injuries; Emergency Department Studies in an International Perspective. Geneva: World Health Organisation, 2009.Connor J, Kypri K, Bell L. Alcohol involvement in aggression between intimate partners in New Zealand: a national cross-sectional study. BMJ Open 2011(doi:10.1136/bmjopen-2011-000065).Chalmers DJ, Fanslow JL, Langley JD. Injury from assault in New Zealand: an increasing public health problem. Aust J Public Health 1995;19(2):149-54.Gawryszewski VP, da Silva MMA, Malta DC, et al. Violence-related injury in emergency departments in Brazil. Rev Panam Salud Publica 2008;24(6):400-8.Sivarajasingam V, Shepherd J, Mathews K, Jones S. Violence-related injury data in England and Wales. British Journal of Criminology 2003;43:223-27.Rand M. Violence-related injuries treated in hospital emergency departments. Washington DC, 1997.Porteous D. Violence now in third generation: Judge. Otago Daily Times 2011.Shepherd J, Sivarajasingam V. Injury research explains conflicting violence trends. Injury Prevention 2005;11(6):324-5.Langley J. Emergency department data suffer similar threats to validity as police data Injury Prevention 2006;12:208.Cryer C, Langley JD, Stephenson SCR, et al. Measure for measure: the quest for valid indicators of non-fatal injury incidence. Public Health 2002;116(5):257-62.Gulliver P, Cryer C, Davie G. Investigation of provisional status of the NZIPS serious non-fatal assault and self harm indicators. Dunedin, 2009.

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

View Article PDF

Assault resulting in injury is a significant public health problem in New Zealand. The most recently available national data indicates assaultive deaths account for 3.5% of all injury deaths and 3.4% of hospital discharges.1,2Assault attracts considerable public and media attention, and is one of six priority areas for the New Zealand Injury Prevention Strategy (NZIPS) 3. A key focus of NZIPS is to cenhance the infrastructure that supports injury prevention activity to improve injury prevention performanced.A recent review of that strategy reported that between 2003 and 2008 there was a 50% increase in the age standardised rates of serious non-fatal assaultive injury 4. However, no further insight was provided concerning the risk factors for, or characteristics of, assaultive injury. Nor has then been any other recent published NZ research that might provide further insight into epidemiological trends of these more serious events.Accordingly we sought to describe the: (1) Distribution of serious non-fatal assault injury for the period 2000-2009 by sociodemographic characteristics, location of incidents, methods used to inflict injury, alcohol involvement, and nature of injury; and (2) Trends in serious assault injury by age, gender, and method. Methods We used the same methods for defining a serious non-fatal assault case as that are used in the NZIPS chartbooks.5 Briefly, this consisted of identifying all cases in the National Minimum Data Set of hospital discharges (NMDS) with: An International Classifications of Diseases and Related Health Problems, version 10, Australian Modification (ICD-10-AM) injury related principal diagnosis (ICD-10-AM diagnosis code S00-T78), (b) where the first cause of injury was recorded as assault (ICD-10-AM external cause codes X85-Y09), Which resulted in injuries which were high-threat to life (6% or more chance of dying), The victim was discharged in the period 2000-2009. Readmissions for follow-up treatment were excluded. Public hospitals provide 99.5% of inpatient treatment of injury in the acute phase. For the purposes of providing a measure of treatment resource impact we estimated the cumulative bed days stay associated with each case. This measure is the sum of the days stayed over the first visit and any subsequent readmission related to the incident. All records which meet the above criteria were searched for ICD-10-AM diagnosis and external cause codes indicative of alcohol involvement using the approach adopted by a US study of non-fatal suicide acts which resulted in hospitalisation.6 Records with ICD-10-AM codes indicating alcohol intoxication [Mental and behavioural disorders due to use of alcohol (F10): acute intoxication (F10.0), harmful use (F10.1) dependence syndrome ( F10.2) residual and late onset psychotic disorder (F10.7), psychotic disorder(F10.5)] were identified. Additional records with external cause of injury codes indicative of accidental poisoning by and exposure to alcohol (X45), intentional poisoning by and exposure to alcohol (X65) or alcohol poisoning intent undetermined (Y15) were also flagged as alcohol involved, as were those with diagnosis codes that included problems related to lifestylealcohol use (Z72.1), and evidence of alcohol involvement as determined by blood alcohol level (Y90.0-Y90.9). Cases were only counted as being alcohol involved once, irrespective of the number of alcohol related diagnosis or external cause of injury codes recorded in the hospital record. The NMDS records self-defined ethnicity in which patients may self-report up to three ethnic groups to which they belong. For those who report multiple ethnicities, the concept of ethnicity for this investigation has been defined in line with NMDS reporting: ethnicity is prioritised with M ori ethnicity receiving the top priority, followed by Pacific Islander, Asian and finally European. Residential area deprivation levels (NZDep2006) were based on the residential address of the assault victim as recorded in the NMDS. NZDep2006 scores are derived from Statistics New Zealand census data and combine measures of income, home ownership, support, employment, qualifications, living space, communication and transport to provide a measure of the relative level of deprivation for census meshblock areas (each meshblock contains approximately 87 people in 2006 and represent the area covered by a single census enumerator). Residential areas are assigned a value on an ordinal score from 1 (least deprived) to 10 (most deprived).7 Assault victims were assigned area deprivation scores based on their residential address. Denominators for rates were obtained from the Statistics New Zealand usually resident population estimates (series 5) for June 30 of the relevant year. Series 5 estimates assume medium fertility, medium mortality and long-run annual net migration of 10,000. For the calculation of ethnic specific rates, Statistics New Zealand population estimates for the relevant ethnic group, as at June 30 of the relevant year was used as the denominator. Ethnic-specific population estimates for M ori, Pacific Island and Asian populations were only available for the period 2006 onwards. These rates were age standardised. Age standardisation was via the direct method with five year age bands from 0-4 years to 85 and 85+ years. The standard population was the New Zealand population 2006 as at June 2006. Calculation of crude rates for NZDep2006 decile categories were based on Statistics New Zealand census area unit population estimates, available for the period 2006 onwards, as at June 30 of the relevant years. Statistics New Zealand provides mapping files that allow meshblocks used in the calculation of NZDep scores to be mapped to larger geographical area units, such as census area unit population estimates. NZDep scores for larger area units are derived from the average NZDep scores of the meshblocks included. 95% confidence intervals for rates assume a Poisson distribution. Ethics approval for this investigation was obtained from the New Zealand Multi-region Ethics Committee (Reference number OTA/99/02/008). Results For the period 2000-2009 inclusive there were 8006 serious non-fatal assaults (average annualised rate of 19.56 per 100,000 per year). Overall males accounted for the bulk (76%) of the burden of assault (Table 1). Males aged 15-24 years had the highest rates of assault. This rate was approximately five times the highest age specific rate for females (25-34 year olds). Table 1. Sociodemographic characteristics of serious non-fatal assaults by gender 2000-2009 Variables Males (n=6,335) Females (n=1671) N % Rate (95%CI) N % Rate (95%CI) Age 0-14 years 15-24 years 25-34 years 35-49 years 50-64 years 65+ years 239 2409 1633 1530 416 108 3.8 38.0 25.8 24.2 6.6 1.7 5.3 (4.6-6.0) 81.6 (78.4-84.9) 61.6 (58.7-64.7) 34.6 (32.9-36.4) 12.7 (11.5-14.0) 4.9 (4.0-5.9) 156 423 463 481 98 50 9.3 25.3 27.7 28.8 5.9 3.0 3.6 (3.1-4.2) 14.7 (13.3-16.2) 16.3 (14.8-17.9) 10.2 (9.3-11.2) 2.9 (2.4-3.6) 1.8 (1.4-2.4) TOTAL 6335 100 1671 100 Ethnicity M ori Pacific Island Asian NZ European/ other 992 429 145 1563 31.7 13.7 4.6 50.0 2006-2009 77.4 (72.3-82.4) 67.8 (60.8-74.7) 14.8 (12.2-17.4) 26.0 (24.7-27.3) 380 72 31 312 47.8 9.1 3.9 39.3 2006-2009 28.0 (24.1-30.9) 11.0 (8.5-13.6) 3.2 (2.0-4.4) 4.8 (4.3-5.4) NZDep 2006 Score 1 (least deprived) 2 3 4 5 6 7 8 9 10 (most deprived) 30 227 420 502 615 633 961 898 1095 519 0.5 3.9 7.1 8.5 10.4 10.7 16.3 15.2 18.6 8.8 Crude rates 2006-2009 2.5 (1.5-3.9) 13.4 (11.1-16.1) 26.8 (23.3-30.7) 27.6 (24.1-31.6) 36.2 (32.3-40.4) 36.1 (32.1-40.5) 56.9 (51.9-62.6) 50.6 (46.2-55.4) 64.9 (59.7-70.4) 31.1 (27.4-35.0) 13 30 100 147 158 140 219 260 336 166 0.8 1.9 6.4 9.4 10.1 8.9 14.0 16.6 21.4 10.6 Crude rates 2006-2009 0.8 (0.2-1.7) 2.4 (1.5-3.7) 6.4 (4.8-8.5) 8.1 (6.2-10.3) 8.2 (6.4-10.3) 7.9 (6.1-10.0) 12.9 (10.7-15.5) 14.1 (11.8-16.6) 17.5 (15.0-20.4) 8.1 (6.4-10.2) For males there was a marked and consistent increase in rates among 15-24 year olds over time (Figure 1). The trend for females in this age group was very variable. The trend for the 25-34 year olds showed a more consistent and marked increase over time (Figure 2). Figure 1. Serious non-fatal assault, annual rates by age group, males only Figure 2. Serious non-fatal assault, annual rates by age group, females only M ori accounted for almost half (48%) of female and one third (32%) of male serious non-fatal assaults (Table 1). Pacific Island people also figured prominently among the male statistics having a rate only slightly lower than M ori males. Between 2006 and 2009 the rates of serious non-fatal assault increased for M ori from 43.6/100,000-62.6/100,000, for Pacific Islanders from 37.3/100,000 to 38.6/100,000, for Asians from 7.7/100,000 to 9.1/100,000 and for New Zealand European/Other from 13.3/100,000 to 15.8/100,000. For both males and females the rates for NZDep groups 7, 8 and 9 were 17-26 times higher than that for the least deprived group for females and 32-39 times higher than the least deprived group for the males. Overall, the home (26%), and the street/highway (18%) were the most common locations of incidents (Table 2). There was a difference in the location of the injury scene by gender, for female victims, 56% of assaultive injury events occurred in the home, in comparison with 20% for male victims; while 24% of assaultive injuries for males occurred in the street/highway compared with 10% for females. There was a high proportion of victims for which no information was recorded about the location of the injury event35.5% of male cases and 24.5% of female cases (Table 2). Table 2. Circumstances of serious non-fatal assaults by gender 2000-2009 Variables Males (n=6335) Females (n=1671) N % N % Injury scene Home Residential institution School/admin Sports/athletics area Street/highway Trade/service area Industrial area Farm Other specified Unspecified 1188 162 88 57 1397 583 20 7 322 2108 20.0 2.7 1.5 1.0 23.6 9.8 0.3 0.1 5.4 35.5 855 15 20 1 156 58 3 0 50 375 55.8 1.0 1.3 0.1 10.2 3.8 0.2 0.0 3.3 24.5 Method Hanging Firearms Smoke Vapours Sharp object Blunt object Bodily force Neglect All other* 14 32 18 13 953 1284 2879 125 1017 0.2 0.5 0.3 0.2 15.0 20.3 45.5 2.0 16.1 41 5 8 12 118 214 820 213 240 2.5 0.3 0.5 0.7 7.0 12.8

Summary

Abstract

Aim

To describe the distribution of, and trends in, the characteristics of serious nonfatal assault injury for the period 2000-2009.

Method

Serious non-fatal hospitalised assault injury for the 2000-2009 period were identified and described by: sociodemographic characteristics, location of incidents, methods used to inflict injury, alcohol involvement, and nature of injury. Trends in assault by age, gender, and method were examined.

Results

Males, 15-24 year olds, Maori, Pacific Islanders, and those from deprived neighbourhoods had markedly elevated assault rates. Assault by bodily force and head injuries predominated with the former being the major category of assault that increased the most over time

Conclusion

There is a disturbing level of serious assault in New Zealand and the situation is getting worse. We need to review current efforts to prevent these incidents.

Author Information

John Langley, Emeritus Professor; Pauline Gulliver, Senior Research Fellow; Injury Prevention Research Unit (http://www.otago.ac.nz/ipru), Dept of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin

Acknowledgements

The authors thank Colin Cryer, Gabrielle Davie and Kypros Kypri for helpful comments on earlier versions of this paper.

Correspondence

J Langley, Injury Prevention Research Unit, Dept of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, PO Box 56, Dunedin 9054, New Zealand. Fax: +64 (0)3 4798337

Correspondence Email

John.langley@otago.ac.nz

Competing Interests

None known.

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