1. Crude CF male suicide rates were calculated from 1995 to 2012 inclusive. Canadian rates for suicide in females are typically 1/3 to 1/5 of those for males. In conjunction with the low proportion of females in the CF, it is not unusual to have very few female suicides in the CF over this short period of time. Due to the very low number of female suicides and instability of this data statistically, comparisons to the Canadian suicide rates were made with male rates alone. Suicide rates prior to 1995 have not been calculated as the method of ascertainment of suicides has changed over the years.
2. To compare CF male rates with general Canadian male population rates, standardization by age using the indirect method was used to provide standardized mortality ratios (SMRs) for suicide up to 2009. This method controls for the age difference between the CF male and general Canadian male populations. An SMR is the observed number of cases divided by the number of cases that would be expected in the population at risk based on the age and sex-specific rates of a standard population (the Canadian population in this case) multiplied by 100. Therefore, an SMR less than 100% indicates that the population in question has a lower rate than the Canadian population, while an SMR greater than 100% indicates a higher rate.
3. The calculation of confidence intervals for population-based data is controversial but is provided here for those who may want to generalize the results to other years. Confidence intervals (CIs) were calculated for CF male suicide rates and SMRs directly using Poisson distribution 95% confidence limits using the exact method described by Breslow and Day 1. In any case, CIs are valuable in illustrating the variability that is possible when dealing with such small numbers of cases.
4. SMRs were calculated separately for those with and without a history of deployment. However, SMRs cannot be compared directly to each other as they are standardized to different population distributions.
5. To compare suicide risk among those with a history of deployment directly to those without, direct standardization was done using the total male population of the CF as the standard. Age-adjusted suicide rates for those with and without a history of deployment were compared using rate ratios. However, since age and sex-specific rates for this population are extremely unstable, caution should be used when comparing directly standardized rates. Confidence intervals were calculated using the method described in the text by Rothman and Greenland 2.
6. Information on the number of suicides and demographic information was obtained from the Directorate of Casualty Support Management (DCSM) up to 2011. As of 2012, the number of suicides were provided by the Administrative Investigation Support Centre (AISC). Note that suicide death investigations often take several months, as a result the investigations into suicides in the previous year are not complete at the time of the initial release of this report. As a result, the number of suicides can change, for this report the number of suicide deaths for 2011 has been increased by 2 from the previous report. Information on deployment history and CF population data (by age, sex and deployment history) originated from the Directorate of Human Resources Information Management (DHRIM). History of deployment was based on department IDs and deployment units from DHRIM. It should be noted that the number of personnel with a history of deployment occasionally changes from previous reports due to updating of DHRIM records; some deployment inaccuracies may persist.
7. Canadian suicide counts by age and sex were obtained from Statistics Canada. Data were available up to 2009 at the time of preparation of this report. Canadian suicide rates are derived from death certificate data. Codes utilized for this report were ICD-9 E950-E959 (suicide and self-inflicted injury) in the Shelf Tables produced by Statistics Canada from 1995 to 1999. For 2000 to 2008 the number of suicide deaths was based on ICD-10 codes X60-84 and Y87.0 utilizing CANSIM Table 102-0540 from Statistics Canada, for 2009 suicide deaths CANSIM Table 102-0551 was the source. Open verdict cases (ICD-9: E980-E989; ICD-10: Y30-Y34) are excluded by Statistics Canada, although they are routinely included in suicide statistics reported elsewhere (e.g. UK – both in civilian and military contexts). All Canadian population denominators were taken from Statistics Canada CANSIM Table 051-0001. Denominators up to and including 2005 were final intercensal estimates and 2006 to 2009 were final postcensal estimates. There is some evidence that death certificate data underestimate suicide rates although the true rate is probably no more than 1.25 times the official rate (CDC National Center for Injury Prevention and Control estimate).