Downloaded from http://injuryprevention.bmj.com/ on January 30, 2016 - Published by group.bmj.com
Brief report
Suicide in Canada: impact of injuries with undetermined intent on regional rankings Nathalie Auger,1,2 Stephanie Burrows,2 Philippe Gamache,1 Denis Hamel1 1
Institut national de santé publique du Québec, Montreal, Canada 2 University of Montreal Hospital Research Centre, Montreal, Canada Correspondence to Dr Nathalie Auger, 190 Crémazie E Blvd, Montreal, Quebec, Canada H2P 1E2 [email protected] Received 20 March 2015 Revised 8 June 2015 Accepted 22 June 2015 Published Online First 8 July 2015
ABSTRACT The impact of underreporting or misclassifying suicides as injuries with undetermined intent is rarely evaluated. We assessed whether undetermined injury deaths influenced provincial rankings of suicide in Canada, using 2 735 152 Canadians followed for mortality from 1991 to 2001. We found that suicide rates increased by up to 26.5% for men and 37.7% for women after including injuries with undetermined intent, shifting provincial rankings of suicide. Attention to the stigma of suicide and to coding suicides as injuries with undetermined intent is merited for surveillance and prevention.
INTRODUCTION
To cite: Auger N, Burrows S, Gamache P, et al. Inj Prev 2016;22: 76–78. 76
Suicide is the leading cause of death for young people in high-income countries.1 Suicide is monitored routinely in many countries, with regional comparisons used to guide prevention. However, suicide registration is a complex procedure and differences in coding practises can have a large impact on suicide rates.2 Suicides can be disguised by victims or masked by families because of social, religious, financial or political concerns and may be misclassified as other causes of death, often injuries of ‘undetermined intent’.2–5 Variability in suicide statistics may be influenced by procedures for identifying cause of death, criteria defining suicide and cultural context.4 6 Medical examiners and coroners have different approaches and circumstances and may further affect suicide certification.7 8 In Canada, some regions attempt to minimise the number of deaths classified as injuries of undetermined intent. Coroners in Quebec, for instance, carefully investigate deaths from injuries not to miss suicides, and go so far as to identify any potentially disguised as accidents due to drowning, poisoning or road traffic injuries.9 Quebec is known for a high suicide rate10 and few injuries of undetermined intent. Suicide rates have been shown to be underestimated in provinces such as Newfoundland and Ontario,11 12 but not much is known on the frequency of injuries of undetermined intent. Inappropriate classification of injury deaths as ‘undetermined’ has the potential to underestimate suicide rates and affect regional or country rankings.6 The objective of this study was to determine how suicide rates change across Canada when the definition of suicide is broadened to include undetermined injury deaths. In 2004– 2006, men in Canada had 18.0 suicides and 2.6 injury deaths of undetermined intent and women had 5.1 suicides and 0.6 of undetermined intent, per 100 000.13
METHODS We used data from the Canadian Census Mortality Follow-up Study, containing 2 735 152 individuals followed up for mortality from 1991 to 2001.14 The cohort includes 15% of non-institutionalised Canadians aged 25 years and over in 1991. We had data for nine provinces, including from west to east, British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, Newfoundland, Nova Scotia, New Brunswick and the Territories. The province of Prince Edward Island had few suicides and was grouped with Newfoundland. Similarly, the Territories of Nunavut, the Yukon and the Northwest were grouped. We used International Classification of Disease (ICD) codes for principal cause of death to identify suicides (E950–E959, X60–X84, Y87.0) and deaths from injuries of undetermined intent (E980–E989, Y10–Y34, Y87.2, Y89.9). In 2000, the 10th revision of the ICD was implemented. We calculated age-adjusted mortality rates (95% CIs) per 100 000 using two definitions of suicide, one consisting of ICD codes for suicide only and the other combining codes for suicide with injuries of undetermined intent. We determined the absolute increase in the suicide rate when undetermined deaths were included and the per cent increase using the formula, 1−suicide rate/(suicide+undetermined rate).15 To ensure that comparisons were not affected by sociodemographic factors, we estimated the association (HR, 95% CI) between region and risk of suicide using Cox regression models adjusted for age (25–34, 35–44,…, 75–84, ≥85 years), marital status (legally married, common-law, never married, separated/divorced/widowed), education (university, postsecondary, high school, no diploma), income quintile (ratio of family income to low-income cut-off), employment (employed, unemployed, not in labour force), visible minority (no, yes), immigration (no, yes 10 years) and rural residence (metropolitan area, smaller urban area, rural).14 We compared each region with Ontario, the largest province. Follow-up began 4 June 1991, the day of the Census, and ended 31 December 2001. We used days-on-study as the time scale and censored deaths from other causes. We verified the proportional hazard assumption with log (−log survival) plots.
RESULTS Of 260 820 deaths during the study, 3393 were suicides (1.3%) and 702 injuries of undetermined intent (0.3%). The ratio of suicides to undetermined deaths was greater for men (5.0) than for women (4.4), indicating that women were slightly more likely to receive codes for injury with
Auger N, et al. Inj Prev 2016;22:76–78. doi:10.1136/injuryprev-2015-041613
Downloaded from http://injuryprevention.bmj.com/ on January 30, 2016 - Published by group.bmj.com
Brief report undetermined intent. Including undetermined deaths in the definition led to an increase in the suicide rate for nearly every region, except women in the Territories (table 1). Rates increased by up to 9.2 for men and 2.0 for women per 100 000. The largest absolute and per cent increases were for men in Alberta and the Territories and women in Alberta and Manitoba. The general ranking of regions changed little, but the Territories moved into first place before Quebec for the highest male suicide rate, and Alberta moved into second place after the Territories for the highest female suicide rate. In sensitivity analyses, Cox regression models adjusted for individual characteristics suggested little change in the direction of association between region and suicide risk for the two definitions of suicide, although the magnitude of HRs changed slightly relative to Ontario (table 2). Thus, regional rankings of suicide rates changed upon inclusion of deaths due to undetermined injuries, but not enough to have a major impact on HRs of suicide adjusted for individual characteristics.
DISCUSSION In this study, suicide rates in most of Canada increased noticeably when injuries of undetermined intent were included in suicide statistics. This increase affected regional rankings, calling into question the renown that some regions have for very high suicide rates.9 Men in the Territories had higher suicide rates than Quebec when injuries with undetermined intent were included, and men in Alberta vied more closely with Quebec for the number two position. In Canada, provinces used codes for injuries of undetermined intent unequally, suggesting that suicide rates may be disproportionately underestimated in some regions. These findings have implications for surveillance and prevention of suicides and injuries of undetermined intent, two outcomes that are closely intertwined.
Few countries account for misclassification in surveillance of suicide. The UK to our knowledge is the only country that routinely includes injury deaths of undetermined intent in suicide statistics.3 16 In Taiwan, researchers included injuries of undetermined intent in a study of leading methods of suicide, to avoid bias in under-reporting between regions.17 Other research has focused on how suicide misclassification affects international comparisons, especially in Western countries.3 8 13 Interestingly, Islamic countries that proscribe suicide may inordinately misclassify cases as injuries of undetermined intent.18 Misclassification may also affect temporal trends in suicide. In Poland, rates increased over time for both suicide and deaths of undetermined intent, suggesting that the overall burden of suicide is underestimated in the region.19 There is also emerging work suggesting that increasing rates of poisoning deaths and decreasing rates of autopsy lead to more misclassification of suicides with time.8 In South Africa, poisoning, jumping and railway suicides are more likely to be misclassified than other methods.5 Future research would benefit from determining the implications of misclassification for leading methods of suicide in other counties. This study aimed to assess the impact that injuries of undetermined intent have on suicide mortality rates, but could not determine the extent to which suicides may have been misclassified as accidents. Some countries disproportionately misclassify suicides as accidental poisonings or drownings.20 Furthermore, we were limited by the likelihood that a proportion of injuries of undetermined intent were not suicides. Thus, the results we report should not be considered definitive suicide rates, but serve rather to sensitise researchers and practitioners to underreporting, along with the possible impact on estimates routinely used to measure the burden of suicide and to allot resources for prevention.
Table 1 Suicide mortality in Canada according to definition of cause of death, 1991–2001* Suicide
Men British Columbia Alberta Saskatchewan Manitoba Ontario Quebec Newfoundland Nova Scotia New Brunswick† Territories Women British Columbia Alberta Saskatchewan Manitoba Ontario Quebec Newfoundland Nova Scotia New Brunswick† Territories
Suicide plus undetermined
Rate increase
Rate (95% CI)
Rank
Rate (95% CI)
Rank
Absolute
Per cent
16.3 (14.5 to 18.4) 23.3 (20.8 to 26.1) 16.4 (13.2 to 20.3) 18.4 (15.2 to 22.2) 15.3 (14.2 to 16.4) 27.2 (25.5 to 29.0) 11.7 (8.0 to 17.0) 18.6 (15.0 to 23.2) 22.3 (18.1 to 27.4) 25.5 (17.6 to 36.8)
8 3 7 6 9 1 10 5 4 2
19.6 29.9 19.5 23.5 18.8 31.0 13.4 23.7 24.8 34.7
(17.6 to 21.9) (27.0 to 33.1) (16.0 to 23.8) (19.9 to 27.8) (17.6 to 20.0) (29.2 to 32.9) (9.6 to 18.8) (19.5 to 28.7) (20.4 to 30.2) (25.7 to 46.9)
7 3 8 6 9 2 10 5 4 1
3.3 6.6 3.1 5.1 3.5 3.8 1.7 5.1 2.5 9.2
16.8 22.1 15.9 21.7 18.6 12.3 12.7 21.5 10.1 26.5
5.6 (4.5 to 6.8) 6.6 (5.3 to 8.3) 4.3 (2.6 to 6.9) 3.3 (2.0 to 5.5) 4.1 (3.6 to 4.7) 7.0 (6.2 to 8.0) ‡ 3.9 (2.3 to 6.6) 2.2 (1.2 to 4.2) 17.2 (10.5 to 28.2)
4 3 5 8 6 2 – 7 9 1
6.4 (5.3 to 7.7) 8.8 (7.3 to 10.6) 5.1 (3.3 to 7.9) 5.3 (3.7 to 7.5) 5.5 (4.9 to 6.2) 8.0 (7.1 to 9.0) 1.4 (0.3 to 5.6) 4.5 (2.7 to 7.4) 3.7 (2.0 to 6.6) 17.2 (10.5 to 28.2)
4 2 7 6 5 3 10 8 9 1
0.8 2.2 0.8 2.0 1.4 1.0 – 0.6 1.5 0
12.5 25.0 15.7 37.7 25.5 12.5 – 13.3 40.5 0
*Age-adjusted rates per 100 000 person-years. †Includes the province of Prince Edward Island. ‡Not reported to conform to data privacy regulations in Canada.
Auger N, et al. Inj Prev 2016;22:76–78. doi:10.1136/injuryprev-2015-041613
77
Downloaded from http://injuryprevention.bmj.com/ on January 30, 2016 - Published by group.bmj.com
Brief report Table 2 Association between region and suicide risk according to definition of cause of death HR* (95% CI) Suicide Men British Columbia Alberta Saskatchewan Manitoba Ontario Quebec Newfoundland Nova Scotia New Brunswick† Territories Women British Columbia Alberta Saskatchewan Manitoba Ontario Quebec Newfoundland Nova Scotia New Brunswick† Territories
Suicide plus undetermined
1.0 (0.9 1.4 (1.2 0.9 (0.7 1.0 (0.8 Ref 1.5 (1.4 0.5 (0.4 1.0 (0.8 1.1 (0.9 1.3 (0.9
to 1.2) to 1.6) to 1.1) to 1.3)
1.3 (1.0 1.6 (1.3 1.0 (0.7 0.8 (0.5 Ref 1.4 (1.2 0.2 (0.1 0.8 (0.5 0.7 (0.4 1.5 (0.7
to 1.7) to 2.1) to 1.6) to 1.2)
to 1.7) to 0.8) to 1.3) to 1.4) to 1.9)
to 1.7) to 0.7) to 1.4) to 1.2) to 3.1)
1.0 (0.9 to 1.1) 1.5 (1.3 to 1.7) 0.9 (0.7 to 1.1) 1.1 (0.9 to 1.3) Ref 1.4 (1.3 to 1.5) 0.5 (0.4 to 1.3) 1.0 (0.9 to 1.3) 1.0 (0.9 to 1.3) 1.3 (1.0 to 1.8) 1.1 (0.9 to 1.4) 1.6 (1.3 to 2.0) 0.9 (0.6 to 1.3) 0.9 (0.6 to 1.3) Ref 1.2 (1.0 to 1.4) 0.2 (0.1 to 0.6) 0.7 (0.5 to 1.1) 0.6 (0.4 to 1.0) 1.1 (0.5 to 2.2)
*Adjusted for age, marital status, education, income, employment, visible minority, immigration and rural residence. †Includes the province of Prince Edward Island.
Acknowledgements NA and SB acknowledge career awards from the Fonds de recherche du Québec-Santé. Contributors All authors contributed substantially to study conception, design, analysis and interpretation of data; drafting or revision of the manuscript and approval of final version. NA conceived and designed the study with SB. PG and DH analysed the data and NA and SB interpreted the results. NA wrote the manuscript and SB and PG revised it for important intellectual content. All authors approved the final version of the manuscript. Funding Funding for the Census Mortality Follow-up Study was provided by the Canadian Population Health Initiative. Competing interests None declared. Provenance and peer review Not commissioned; externally peer reviewed.
REFERENCES 1
2 3
4 5
6 7
8 9
Suicide is a stigma and families may mask the true reason for a death. Suicides have the potential to be reported as injuries of undetermined intent or even accidental poisonings or drownings.2–8 Reluctance to report suicides is under recognised in public health, and the impact on country rankings and prevention merits attention.
10
11
What is already known on this subject ▸ Suicides may be under-reported or misclassified as injuries with undetermined intent. ▸ The impact of under-reporting on estimates of suicide rates in countries is unclear.
12 13
14 15 16
What this study adds ▸ In Canada, under-reporting potentially lowers suicide rates by 10%–38%. ▸ Under-reporting affects the ranking of suicide rates across provinces. ▸ Better recording is needed to improve suicide surveillance and prevention.
78
17 18
19
20
World Health Organization. Preventing suicide: a global imperative. Geneva: WHO, 2014. http://apps.who.int/iris/bitstream/10665/131056/1/9789241564779_eng.pdf (accessed 17 Mar 2015). O’Carroll P. A consideration of the validity and reliability of suicide mortality data. Suicide Life Threat Behav 1989;19:1–16. Värnik P, Sisask M, Värnik A, et al. Validity of suicide statistics in Europe in relation to undetermined deaths: developing the 2–20 benchmark. Inj Prev 2012;18:321–5. Burrows S, Laflamme L. Determination of suicide in South Africa: medical practitioner perspectives. Arch Suicide Res 2007;11:281–90. Burrows S, Laflamme L. Assessment of accuracy of suicide mortality surveillance data in South Africa: investigation in an urban setting. Crisis 2007;28:74–81. Jougla E, Pequignot F, Chappert J, et al. Quality of suicide mortality data. Rev Epidemiol Sante Publique 2002;50:49–62. Lu TH, Sun SM, Huang SM, et al. Mind your manners: quality of manner of death certification among medical examiners and coroners in Taiwan. Am J Forensic Med Pathol 2006;27:352–4. Rockett IRH, Kapusta ND, Bhandari R. Suicide misclassification in an international context: revisitation and update. Suicidology Online 2011;2:48–61. St-Laurent D, Bouchard C. L’épidémiologie du suicide au Québec: que savons-nous de la situation récente? Québec: Institut national de santé publique du Québec, 2004. http://www.inspq.qc.ca/pdf/publications/283-FeuilletEpidemioSuicide.pdf. http://apps.who.int/iris/bitstream/10665/131056/1/9789241564779_eng.pdf (accessed 17 Mar 2015). Légaré G, Gagné M, Perron PA. La mortalité par suicide au Québec: 1981 à 2012 —Mise à jour 2015. Québec: Institut national de santé publique du Québec, 2015. http://www.inspq.qc.ca/pdf/publications/1939_Mortalite_Suicide_2015.pdf. http:// apps.who.int/iris/bitstream/10665/131056/1/9789241564779_eng.pdf (accessed 17 Mar 2015). Edwards N, Alaghehbandan R, MacDonald D, et al. Suicide in Newfoundland and Labrador: a linkage study using medical examiner and vital statistics data. Can J Psychiatry 2008;53:252–9. Parai JL, Kreiger N, Tomlinson G, et al. The validity of the certification of manner of death by Ontario coroners. Ann Epidemiol 2006;16:805–11. Pritchard C, Hansen L. Examining undetermined and accidental deaths as source of ‘under-reported-suicide’ by age abd sex in twenty western countries. Community Ment Health J 2015;51:365–76. Wilkins R, Tjepkema M, Mustard C, et al. The Canadian census mortality follow-up study, 1991 through 2001. Health Rep 2008;19:25–43. Speechley M, Stavraky KM. The adequacy of suicide statistics for use in epidemiology and public health. Can J Public Health 1991;82:38–42. Department of Health. Suicide prevention strategy for England. London, 2012. https://www.gov.uk/government/publications/suicide-prevention-strategy-launched (accessed 2 Jun 2015). Lin JJ, Chang SS, Lu TH. The leading methods of suicide in Taiwan, 2002–2008. BMC Public Health 2010;10;480. Pritchard C, Amanullah S. An analysis of suicide and undetermined deaths in 17 predominantly Islamic countries contrasted with the UK. Psychol Med 2007;37:421–30. Höfer P, Rockett IR, Värnik P, et al. Forty years of increasing suicide mortality in Poland: Undercounting amidst a hanging epidemic? BMC Public Health 2012;12:644. Rockett IR, Thomas BM. Reliability and sensitivity of suicide certification in higher-income countries. Suicide and Life Threat Behav 1999;29:141–9.
Auger N, et al. Inj Prev 2016;22:76–78. doi:10.1136/injuryprev-2015-041613
Downloaded from http://injuryprevention.bmj.com/ on January 30, 2016 - Published by group.bmj.com
Suicide in Canada: impact of injuries with undetermined intent on regional rankings Nathalie Auger, Stephanie Burrows, Philippe Gamache and Denis Hamel Inj Prev 2016 22: 76-78 originally published online July 8, 2015
doi: 10.1136/injuryprev-2015-041613 Updated information and services can be found at: http://injuryprevention.bmj.com/content/22/1/76
These include:
References Email alerting service
Topic Collections
This article cites 16 articles, 2 of which you can access for free at: http://injuryprevention.bmj.com/content/22/1/76#BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Articles on similar topics can be found in the following collections Suicide (public health) (202) Suicide/Self harm (injury) (202) Epidemiologic studies (834)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
Brief report
Suicide in Canada: impact of injuries with undetermined intent on regional rankings Nathalie Auger,1,2 Stephanie Burrows,2 Philippe Gamache,1 Denis Hamel1 1
Institut national de santé publique du Québec, Montreal, Canada 2 University of Montreal Hospital Research Centre, Montreal, Canada Correspondence to Dr Nathalie Auger, 190 Crémazie E Blvd, Montreal, Quebec, Canada H2P 1E2 [email protected] Received 20 March 2015 Revised 8 June 2015 Accepted 22 June 2015 Published Online First 8 July 2015
ABSTRACT The impact of underreporting or misclassifying suicides as injuries with undetermined intent is rarely evaluated. We assessed whether undetermined injury deaths influenced provincial rankings of suicide in Canada, using 2 735 152 Canadians followed for mortality from 1991 to 2001. We found that suicide rates increased by up to 26.5% for men and 37.7% for women after including injuries with undetermined intent, shifting provincial rankings of suicide. Attention to the stigma of suicide and to coding suicides as injuries with undetermined intent is merited for surveillance and prevention.
INTRODUCTION
To cite: Auger N, Burrows S, Gamache P, et al. Inj Prev 2016;22: 76–78. 76
Suicide is the leading cause of death for young people in high-income countries.1 Suicide is monitored routinely in many countries, with regional comparisons used to guide prevention. However, suicide registration is a complex procedure and differences in coding practises can have a large impact on suicide rates.2 Suicides can be disguised by victims or masked by families because of social, religious, financial or political concerns and may be misclassified as other causes of death, often injuries of ‘undetermined intent’.2–5 Variability in suicide statistics may be influenced by procedures for identifying cause of death, criteria defining suicide and cultural context.4 6 Medical examiners and coroners have different approaches and circumstances and may further affect suicide certification.7 8 In Canada, some regions attempt to minimise the number of deaths classified as injuries of undetermined intent. Coroners in Quebec, for instance, carefully investigate deaths from injuries not to miss suicides, and go so far as to identify any potentially disguised as accidents due to drowning, poisoning or road traffic injuries.9 Quebec is known for a high suicide rate10 and few injuries of undetermined intent. Suicide rates have been shown to be underestimated in provinces such as Newfoundland and Ontario,11 12 but not much is known on the frequency of injuries of undetermined intent. Inappropriate classification of injury deaths as ‘undetermined’ has the potential to underestimate suicide rates and affect regional or country rankings.6 The objective of this study was to determine how suicide rates change across Canada when the definition of suicide is broadened to include undetermined injury deaths. In 2004– 2006, men in Canada had 18.0 suicides and 2.6 injury deaths of undetermined intent and women had 5.1 suicides and 0.6 of undetermined intent, per 100 000.13
METHODS We used data from the Canadian Census Mortality Follow-up Study, containing 2 735 152 individuals followed up for mortality from 1991 to 2001.14 The cohort includes 15% of non-institutionalised Canadians aged 25 years and over in 1991. We had data for nine provinces, including from west to east, British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, Newfoundland, Nova Scotia, New Brunswick and the Territories. The province of Prince Edward Island had few suicides and was grouped with Newfoundland. Similarly, the Territories of Nunavut, the Yukon and the Northwest were grouped. We used International Classification of Disease (ICD) codes for principal cause of death to identify suicides (E950–E959, X60–X84, Y87.0) and deaths from injuries of undetermined intent (E980–E989, Y10–Y34, Y87.2, Y89.9). In 2000, the 10th revision of the ICD was implemented. We calculated age-adjusted mortality rates (95% CIs) per 100 000 using two definitions of suicide, one consisting of ICD codes for suicide only and the other combining codes for suicide with injuries of undetermined intent. We determined the absolute increase in the suicide rate when undetermined deaths were included and the per cent increase using the formula, 1−suicide rate/(suicide+undetermined rate).15 To ensure that comparisons were not affected by sociodemographic factors, we estimated the association (HR, 95% CI) between region and risk of suicide using Cox regression models adjusted for age (25–34, 35–44,…, 75–84, ≥85 years), marital status (legally married, common-law, never married, separated/divorced/widowed), education (university, postsecondary, high school, no diploma), income quintile (ratio of family income to low-income cut-off), employment (employed, unemployed, not in labour force), visible minority (no, yes), immigration (no, yes 10 years) and rural residence (metropolitan area, smaller urban area, rural).14 We compared each region with Ontario, the largest province. Follow-up began 4 June 1991, the day of the Census, and ended 31 December 2001. We used days-on-study as the time scale and censored deaths from other causes. We verified the proportional hazard assumption with log (−log survival) plots.
RESULTS Of 260 820 deaths during the study, 3393 were suicides (1.3%) and 702 injuries of undetermined intent (0.3%). The ratio of suicides to undetermined deaths was greater for men (5.0) than for women (4.4), indicating that women were slightly more likely to receive codes for injury with
Auger N, et al. Inj Prev 2016;22:76–78. doi:10.1136/injuryprev-2015-041613
Downloaded from http://injuryprevention.bmj.com/ on January 30, 2016 - Published by group.bmj.com
Brief report undetermined intent. Including undetermined deaths in the definition led to an increase in the suicide rate for nearly every region, except women in the Territories (table 1). Rates increased by up to 9.2 for men and 2.0 for women per 100 000. The largest absolute and per cent increases were for men in Alberta and the Territories and women in Alberta and Manitoba. The general ranking of regions changed little, but the Territories moved into first place before Quebec for the highest male suicide rate, and Alberta moved into second place after the Territories for the highest female suicide rate. In sensitivity analyses, Cox regression models adjusted for individual characteristics suggested little change in the direction of association between region and suicide risk for the two definitions of suicide, although the magnitude of HRs changed slightly relative to Ontario (table 2). Thus, regional rankings of suicide rates changed upon inclusion of deaths due to undetermined injuries, but not enough to have a major impact on HRs of suicide adjusted for individual characteristics.
DISCUSSION In this study, suicide rates in most of Canada increased noticeably when injuries of undetermined intent were included in suicide statistics. This increase affected regional rankings, calling into question the renown that some regions have for very high suicide rates.9 Men in the Territories had higher suicide rates than Quebec when injuries with undetermined intent were included, and men in Alberta vied more closely with Quebec for the number two position. In Canada, provinces used codes for injuries of undetermined intent unequally, suggesting that suicide rates may be disproportionately underestimated in some regions. These findings have implications for surveillance and prevention of suicides and injuries of undetermined intent, two outcomes that are closely intertwined.
Few countries account for misclassification in surveillance of suicide. The UK to our knowledge is the only country that routinely includes injury deaths of undetermined intent in suicide statistics.3 16 In Taiwan, researchers included injuries of undetermined intent in a study of leading methods of suicide, to avoid bias in under-reporting between regions.17 Other research has focused on how suicide misclassification affects international comparisons, especially in Western countries.3 8 13 Interestingly, Islamic countries that proscribe suicide may inordinately misclassify cases as injuries of undetermined intent.18 Misclassification may also affect temporal trends in suicide. In Poland, rates increased over time for both suicide and deaths of undetermined intent, suggesting that the overall burden of suicide is underestimated in the region.19 There is also emerging work suggesting that increasing rates of poisoning deaths and decreasing rates of autopsy lead to more misclassification of suicides with time.8 In South Africa, poisoning, jumping and railway suicides are more likely to be misclassified than other methods.5 Future research would benefit from determining the implications of misclassification for leading methods of suicide in other counties. This study aimed to assess the impact that injuries of undetermined intent have on suicide mortality rates, but could not determine the extent to which suicides may have been misclassified as accidents. Some countries disproportionately misclassify suicides as accidental poisonings or drownings.20 Furthermore, we were limited by the likelihood that a proportion of injuries of undetermined intent were not suicides. Thus, the results we report should not be considered definitive suicide rates, but serve rather to sensitise researchers and practitioners to underreporting, along with the possible impact on estimates routinely used to measure the burden of suicide and to allot resources for prevention.
Table 1 Suicide mortality in Canada according to definition of cause of death, 1991–2001* Suicide
Men British Columbia Alberta Saskatchewan Manitoba Ontario Quebec Newfoundland Nova Scotia New Brunswick† Territories Women British Columbia Alberta Saskatchewan Manitoba Ontario Quebec Newfoundland Nova Scotia New Brunswick† Territories
Suicide plus undetermined
Rate increase
Rate (95% CI)
Rank
Rate (95% CI)
Rank
Absolute
Per cent
16.3 (14.5 to 18.4) 23.3 (20.8 to 26.1) 16.4 (13.2 to 20.3) 18.4 (15.2 to 22.2) 15.3 (14.2 to 16.4) 27.2 (25.5 to 29.0) 11.7 (8.0 to 17.0) 18.6 (15.0 to 23.2) 22.3 (18.1 to 27.4) 25.5 (17.6 to 36.8)
8 3 7 6 9 1 10 5 4 2
19.6 29.9 19.5 23.5 18.8 31.0 13.4 23.7 24.8 34.7
(17.6 to 21.9) (27.0 to 33.1) (16.0 to 23.8) (19.9 to 27.8) (17.6 to 20.0) (29.2 to 32.9) (9.6 to 18.8) (19.5 to 28.7) (20.4 to 30.2) (25.7 to 46.9)
7 3 8 6 9 2 10 5 4 1
3.3 6.6 3.1 5.1 3.5 3.8 1.7 5.1 2.5 9.2
16.8 22.1 15.9 21.7 18.6 12.3 12.7 21.5 10.1 26.5
5.6 (4.5 to 6.8) 6.6 (5.3 to 8.3) 4.3 (2.6 to 6.9) 3.3 (2.0 to 5.5) 4.1 (3.6 to 4.7) 7.0 (6.2 to 8.0) ‡ 3.9 (2.3 to 6.6) 2.2 (1.2 to 4.2) 17.2 (10.5 to 28.2)
4 3 5 8 6 2 – 7 9 1
6.4 (5.3 to 7.7) 8.8 (7.3 to 10.6) 5.1 (3.3 to 7.9) 5.3 (3.7 to 7.5) 5.5 (4.9 to 6.2) 8.0 (7.1 to 9.0) 1.4 (0.3 to 5.6) 4.5 (2.7 to 7.4) 3.7 (2.0 to 6.6) 17.2 (10.5 to 28.2)
4 2 7 6 5 3 10 8 9 1
0.8 2.2 0.8 2.0 1.4 1.0 – 0.6 1.5 0
12.5 25.0 15.7 37.7 25.5 12.5 – 13.3 40.5 0
*Age-adjusted rates per 100 000 person-years. †Includes the province of Prince Edward Island. ‡Not reported to conform to data privacy regulations in Canada.
Auger N, et al. Inj Prev 2016;22:76–78. doi:10.1136/injuryprev-2015-041613
77
Downloaded from http://injuryprevention.bmj.com/ on January 30, 2016 - Published by group.bmj.com
Brief report Table 2 Association between region and suicide risk according to definition of cause of death HR* (95% CI) Suicide Men British Columbia Alberta Saskatchewan Manitoba Ontario Quebec Newfoundland Nova Scotia New Brunswick† Territories Women British Columbia Alberta Saskatchewan Manitoba Ontario Quebec Newfoundland Nova Scotia New Brunswick† Territories
Suicide plus undetermined
1.0 (0.9 1.4 (1.2 0.9 (0.7 1.0 (0.8 Ref 1.5 (1.4 0.5 (0.4 1.0 (0.8 1.1 (0.9 1.3 (0.9
to 1.2) to 1.6) to 1.1) to 1.3)
1.3 (1.0 1.6 (1.3 1.0 (0.7 0.8 (0.5 Ref 1.4 (1.2 0.2 (0.1 0.8 (0.5 0.7 (0.4 1.5 (0.7
to 1.7) to 2.1) to 1.6) to 1.2)
to 1.7) to 0.8) to 1.3) to 1.4) to 1.9)
to 1.7) to 0.7) to 1.4) to 1.2) to 3.1)
1.0 (0.9 to 1.1) 1.5 (1.3 to 1.7) 0.9 (0.7 to 1.1) 1.1 (0.9 to 1.3) Ref 1.4 (1.3 to 1.5) 0.5 (0.4 to 1.3) 1.0 (0.9 to 1.3) 1.0 (0.9 to 1.3) 1.3 (1.0 to 1.8) 1.1 (0.9 to 1.4) 1.6 (1.3 to 2.0) 0.9 (0.6 to 1.3) 0.9 (0.6 to 1.3) Ref 1.2 (1.0 to 1.4) 0.2 (0.1 to 0.6) 0.7 (0.5 to 1.1) 0.6 (0.4 to 1.0) 1.1 (0.5 to 2.2)
*Adjusted for age, marital status, education, income, employment, visible minority, immigration and rural residence. †Includes the province of Prince Edward Island.
Acknowledgements NA and SB acknowledge career awards from the Fonds de recherche du Québec-Santé. Contributors All authors contributed substantially to study conception, design, analysis and interpretation of data; drafting or revision of the manuscript and approval of final version. NA conceived and designed the study with SB. PG and DH analysed the data and NA and SB interpreted the results. NA wrote the manuscript and SB and PG revised it for important intellectual content. All authors approved the final version of the manuscript. Funding Funding for the Census Mortality Follow-up Study was provided by the Canadian Population Health Initiative. Competing interests None declared. Provenance and peer review Not commissioned; externally peer reviewed.
REFERENCES 1
2 3
4 5
6 7
8 9
Suicide is a stigma and families may mask the true reason for a death. Suicides have the potential to be reported as injuries of undetermined intent or even accidental poisonings or drownings.2–8 Reluctance to report suicides is under recognised in public health, and the impact on country rankings and prevention merits attention.
10
11
What is already known on this subject ▸ Suicides may be under-reported or misclassified as injuries with undetermined intent. ▸ The impact of under-reporting on estimates of suicide rates in countries is unclear.
12 13
14 15 16
What this study adds ▸ In Canada, under-reporting potentially lowers suicide rates by 10%–38%. ▸ Under-reporting affects the ranking of suicide rates across provinces. ▸ Better recording is needed to improve suicide surveillance and prevention.
78
17 18
19
20
World Health Organization. Preventing suicide: a global imperative. Geneva: WHO, 2014. http://apps.who.int/iris/bitstream/10665/131056/1/9789241564779_eng.pdf (accessed 17 Mar 2015). O’Carroll P. A consideration of the validity and reliability of suicide mortality data. Suicide Life Threat Behav 1989;19:1–16. Värnik P, Sisask M, Värnik A, et al. Validity of suicide statistics in Europe in relation to undetermined deaths: developing the 2–20 benchmark. Inj Prev 2012;18:321–5. Burrows S, Laflamme L. Determination of suicide in South Africa: medical practitioner perspectives. Arch Suicide Res 2007;11:281–90. Burrows S, Laflamme L. Assessment of accuracy of suicide mortality surveillance data in South Africa: investigation in an urban setting. Crisis 2007;28:74–81. Jougla E, Pequignot F, Chappert J, et al. Quality of suicide mortality data. Rev Epidemiol Sante Publique 2002;50:49–62. Lu TH, Sun SM, Huang SM, et al. Mind your manners: quality of manner of death certification among medical examiners and coroners in Taiwan. Am J Forensic Med Pathol 2006;27:352–4. Rockett IRH, Kapusta ND, Bhandari R. Suicide misclassification in an international context: revisitation and update. Suicidology Online 2011;2:48–61. St-Laurent D, Bouchard C. L’épidémiologie du suicide au Québec: que savons-nous de la situation récente? Québec: Institut national de santé publique du Québec, 2004. http://www.inspq.qc.ca/pdf/publications/283-FeuilletEpidemioSuicide.pdf. http://apps.who.int/iris/bitstream/10665/131056/1/9789241564779_eng.pdf (accessed 17 Mar 2015). Légaré G, Gagné M, Perron PA. La mortalité par suicide au Québec: 1981 à 2012 —Mise à jour 2015. Québec: Institut national de santé publique du Québec, 2015. http://www.inspq.qc.ca/pdf/publications/1939_Mortalite_Suicide_2015.pdf. http:// apps.who.int/iris/bitstream/10665/131056/1/9789241564779_eng.pdf (accessed 17 Mar 2015). Edwards N, Alaghehbandan R, MacDonald D, et al. Suicide in Newfoundland and Labrador: a linkage study using medical examiner and vital statistics data. Can J Psychiatry 2008;53:252–9. Parai JL, Kreiger N, Tomlinson G, et al. The validity of the certification of manner of death by Ontario coroners. Ann Epidemiol 2006;16:805–11. Pritchard C, Hansen L. Examining undetermined and accidental deaths as source of ‘under-reported-suicide’ by age abd sex in twenty western countries. Community Ment Health J 2015;51:365–76. Wilkins R, Tjepkema M, Mustard C, et al. The Canadian census mortality follow-up study, 1991 through 2001. Health Rep 2008;19:25–43. Speechley M, Stavraky KM. The adequacy of suicide statistics for use in epidemiology and public health. Can J Public Health 1991;82:38–42. Department of Health. Suicide prevention strategy for England. London, 2012. https://www.gov.uk/government/publications/suicide-prevention-strategy-launched (accessed 2 Jun 2015). Lin JJ, Chang SS, Lu TH. The leading methods of suicide in Taiwan, 2002–2008. BMC Public Health 2010;10;480. Pritchard C, Amanullah S. An analysis of suicide and undetermined deaths in 17 predominantly Islamic countries contrasted with the UK. Psychol Med 2007;37:421–30. Höfer P, Rockett IR, Värnik P, et al. Forty years of increasing suicide mortality in Poland: Undercounting amidst a hanging epidemic? BMC Public Health 2012;12:644. Rockett IR, Thomas BM. Reliability and sensitivity of suicide certification in higher-income countries. Suicide and Life Threat Behav 1999;29:141–9.
Auger N, et al. Inj Prev 2016;22:76–78. doi:10.1136/injuryprev-2015-041613
Downloaded from http://injuryprevention.bmj.com/ on January 30, 2016 - Published by group.bmj.com
Suicide in Canada: impact of injuries with undetermined intent on regional rankings Nathalie Auger, Stephanie Burrows, Philippe Gamache and Denis Hamel Inj Prev 2016 22: 76-78 originally published online July 8, 2015
doi: 10.1136/injuryprev-2015-041613 Updated information and services can be found at: http://injuryprevention.bmj.com/content/22/1/76
These include:
References Email alerting service
Topic Collections
This article cites 16 articles, 2 of which you can access for free at: http://injuryprevention.bmj.com/content/22/1/76#BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Articles on similar topics can be found in the following collections Suicide (public health) (202) Suicide/Self harm (injury) (202) Epidemiologic studies (834)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
