Annex C: Most Recent Suicide Surveillance Report from the Directorate of Force Health Protection

Suicide in the Canadian Forces 1995 to 2008

Author: Dr. Jeff Whitehead MD MSc FRCPC
Environmental Occupational Health Surveillance
Directorate of Force Health Protection

Reviewed by: Col HC MacKay MD
Director Force Health Protection

Approved by: Cmdre HW Jung MD
Canadian Forces Surgeon General

D FHP / Epidemiology

17 Sept 2009

 


 

Introduction

There has been concern since the early 1990s about the apparent rate of suicide in the CF and its possible relationship to deployment. As a result, the Surgeon General has been asked to determine the rate of suicide among CF personnel overall in comparison to the Canadian population as well as the rate of suicide in those personnel with a history of deployment compared to those without such a history. Although DND keeps a current record of CF suicides, comparisons with the general Canadian population are dependent on the releases of Canadian mortality rates by Statistics Canada approximately 2 years after the end of data collection. CF suicide data are available until 2008; however, the most recent Canadian data are available until 2005.

This is not the first report on suicide in the CF. A study by Sakinofsky and colleagues in 1996 investigated the suicides of CF personnel between January 1990 and June 1995. This study found the male CF suicide rate to be 12.2/100,000 over the 5.5 years covered by the study compared to the Canadian rate for 20 to 54 year old males of 26.8/100,000. The assumption must have been made that Canadian suicide rates did not change after 1992 as the authors only had 1990 to 1992 Canadian data at the time of the study. The Sakinofsky study also found that deployment was not a risk factor for suicide.

D FHP has updated these findings and provides epidemiological reports on a regular basis that include CF suicide rates over time, comparisons to the general population and suicide analyses according to deployment history. This report only includes Regular Force suicides as Reserve Force records are incomplete for both suicides and those at risk. There is a high turnover for Class A Reservists, and suicides among this group are probably reported and investigated outside the military system unless they are specifically brought to the attention of DND. The number at risk is also uncertain due to the high turnover such that the definition of an active reservist is unclear. Since data on suicide attempts are often incomplete, this report only includes completed suicides. This is in keeping with other occupational health studies.

Method

1. Crude CF male suicide rates were calculated from 1995 to 2008 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 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 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 (SMR) for suicide up to 2005. 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. In any case, CIs are valuable in illustrating the variability that is possible when dealing with such small numbers of cases.

4. Concern has been expressed that those with a history of deployment may have a higher risk of suicide. As a result, 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 in the text by Rothman and Greenland. 1

6. Information on the number of suicides was obtained from the Directorate of Casualty Support Management (DCSM). Demographic information (i.e. age, sex, and deployment history) originated from the Directorate of Human Resources Information Management (DHRIM). History of deployment was based on deployment Unit Identification Codes (UIC) from DHRIM. It should be noted that the number of personnel with a history of deployment back to 1997 has changed from previous reports due to updating of DHRIM records; some deployment inaccuracies may persist.

7. Canadian suicide rates by age and sex were obtained from Statistics Canada. Data were available up to 2005 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 for 1998 and 1999. Prior to those years, suicide rates were taken from a table on the Statistics Canada website. For 2000, 2001, and 2005 the number of suicide deaths were based on ICD-10 codes X60-X84 utilizing CANSIM Table 102-0540 from Statistics Canada; for 2002 Causes of Death 84-208-XIE was used. For 2003 and 2004 suicide deaths were taken from CANSIM 102-0551. The Canadian population denominators were all taken from Statistics Canada publication no. 91-213. Denominators up to and including 2002 were final post-censal/intercensal figures, for 2003 and 2004 these were updated post-censal estimates, for 2005 these were preliminary 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).

Results

A. Crude CF Suicide Rates (1995 – 2008)

Table 1 shows the CF rate for suicide per 100,000 for males. As the number of events was less than 20 in each year, rates were not calculated annually as these would not have been statistically reliable. Therefore 5 year rates have been calculated for 1995-99 and 2000-04 and a 4 year rate for 2005-08. Female rates were not calculated as female suicides were uncommon; there were no suicides in females from 1995 to 2001, there was one in 2002, 2 in 2003, one each in 2006, 2007, and 2008.

Table 1: Male CF Multiyear Suicide Rates (1995-2008)

YearNumber of Male CF PersonnelNumber Male CF SuicidesCF Male Suicide Rate per 105 (95% CI)
1995 62,597 12  
1996 57,608 8  
1997 55,041 13  
1998 54,485 13  
1999 53,134 10  
1995-1999 282,865 pys 56 19.8 (15,26)
2000 51,864 12  
2001 51,008 10  
2002 52,326 9  
2003 53,752 9  
2004 53,871 10  
2000-2004 262,821 pys 50 19.0 (14,25)
2005 53,649 10  
2006 54,308 7  
2007 55,141 9  
2008 55,709 13  
2005-2008 218,807 pys 39 17.8 (13,24)

pys = person years

As can be seen, CF suicide rates have not appreciably changed; the point estimates if anything are decreasing. 

B. Comparison of CF Suicide Rates to Canadian Rates using Standardized Mortality Ratios (1995 – 2005)

As the CF rates are somewhat unstable due to low numbers, the best approach is to compare suicide mortality by estimating the number of cases expected assuming Canadian rates applied to the military population. This method, known as indirect standardization, is used commonly in occupational studies. By dividing the number of observed cases by those expected (using Canadian rates), the standardized mortality ratio (SMR) can be calculated. This does limit calculations up to 2005 as Statistics Canada has only released suicide rates up to that year at present. Five year comparisons were calculated except for 2005 where the annual rate was calculated (Table 2). Since 2005 suicide rates for the Canadian population have recently become available from Statistics Canada, the 2005 data is presented even though limited conclusions can be drawn from such small number of deaths. Deaths from suicide annually in the CF are so few that the SMR for 2005 should be interpreted cautiously as small numbers lead to a greater likelihood that the result is due to chance.

Table 2: Comparison of CF Male Suicide Rates to Canadian Male Rates using Standardized Mortality Ratios (SMRs): 1995-2005

YearAgeNumber of Male CF Personnel (pyrs)Canadian Male Suicide RateExpected # of Male CF SuicidesObserved # of Male SuicidesSMR for Suicide (95% Confidence Intervals)
1995-99 15-19 3,668 19.36 0.71 2  
1995-99 20-24 26,729 26.77 7.15 7  
1995-99 25-44 224,982 28.02 63.04 44  
1995-99 45-64 27,486 25.56 7.03 3  
 Total (1995-99) 77.93 56 72% (54,93)
2000-04 15-19 5,285 14.92 0.79 1  
2000-04 20-24 27,958 21.61 6.04 6  
2000-04 25-44 199,383 23.78 47.42 37  
2000-04 45-64 30,195 24.55 7.41 6  
Total (2000-04) 61.66 50 81% (60,107)
2005 15-19 1,098 13.37 0.15  0  
2005 20-24 6,754 20.13 1.36  1  
2005 25-44 38,047 22.61 8.60  8  
2005 45-64 7,750 24.37 1.89  1  
Total (2005) 12.0 10 83% (40,153)

During 1995 to 1999, the SMR was 72% indicating that the number of CF male suicides was 28% lower than that expected based on Canadian male rates taking the different age distributions into account. This finding was statistically significant as the upper confidence limit was less than 100%. For the 2000 to 2004 time period, there were 19% fewer male suicides than would be expected based on suicide rates seen in the Canadian male population. This finding is not statistically significant as the confidence intervals include 100%. In other words, this finding could be due to chance. Similarly,the 2005 data indicate that the CF male population has a 17% lower suicide rate than the Canadian population after adjusting for the age differences between the populations. This SMR is also not significant and has a very wide confidence interval (wider in comparison to the 5 year estimates)indicating great variability in the SMR.

C. Comparison of CF Suicide Rates by Deployment History to Canadian Rates using Standardized Mortality Ratios (1995 – 2005)

Concern has been expressed that those with a history of deployment may be more likely to die of suicide. The standardized mortality ratios according to a history of deployment are shown in Table 3.

Table 3: Standardized Mortality Ratios for Suicide in the CF Male Population By History of Deployment: 1995-2005

AgeMale CF Suicides With HX of DeploymentMale CF Suicides Without HX of Deployment
ExpectedObservedSMR (95% CI)ExpectedObservedSMR (95% CI)
1995-99
15-19 .01 0   .70 2  
20-24 1.36 2   5.80 5  
25-44 25.74 17   37.30 11  
45-64 2.73 0   4.30 7  
Total 29.84 19 64% (38,99) 48.09 36 77% (54,106)
2000-04
15-19 .01 0   .78 1  
20-24 1.35 1   4.69 5  
25-44 26.28 19   21.14 6  
45-64 3.87 4   3.54 2  
Total 31.52 24 76% (49,113) 30.14 25 86% (56,126)
2005
15-19 0.00 0   .15 0  
20-24 .23 0   1.13 1  
25-44 5.25 4   3.35 4  
45-64 1.12 0   .77 1  
Total 6.60 4 61% (17,155) 5.40 6 111% (41,242)

The SMRs in each of the 5 year time periods indicate that the observed number of male suicides is less than that expected using general Canadian male suicide rates. For example, in the period from 2000 to 2004, the number of suicides among male CF members with a history of deployment was 76% of that expected based on Canadian male suicide rates. For males who did not deploy, the SMR was 86%, indicating that compared to the Canadian population of males of the same age, male personnel who did not deploy were 14% less likely to commit suicide. Neither of these findings is statistically significant however. Furthermore, SMRs should not be compared to each other as they are based on different populations. In 2005, males who had a history of deployment were 39% less likely to die from suicide than Canadian males of the same age; however, this result is not significant. The SMR for CF males who do not have a history of deployment is also not significant, indicating that the rate in the CF population is not statistically higher than the suicide rate in the Canadian population of males the same age. Furthermore, the extremely wide confidence intervals for the 2005 data highlight the variability in the annual data.

D. CF Suicide Rates by Deployment History using Direct Standardization (1995 – 2008)

Table 4 shows the results of the direct standardization. Suicide rate ratios less than 1.0 would suggest that a history of deployment is protective; ratios greater than 1.0 would suggest a harmful effect of deployment.

Table 4: Comparison of CF Suicide Rates by Deployment History using Direct Standardization (1995-2008)

AgeTotal Male CF Person-YearsCF Male Suicide Rate Per 100,000Age Adjusted Suicide Rate Per 100,000Suicide Rate Ratio (95% CI)
Hx of DeplNo Hx of DeplHx of DeplNo Hx of Depl
1995-1999
15-19 3,668 0 55.34      
20-24 26,729 39.38 23.09      
25-44 224,982 18.51 20.28      
45-64 27,486 0 17.83      
Total 282,865 17.65 21.12 18.4 20.8 .89 (0.50,1.57)
2000-2004
15-19 5,285 0 19.25      
20-24 27,958 15.95 23.05      
25-44 199,383 17.19 20.25      
45-64 30,195 25.36 13.86      
Total 262,821 18.09 19.97 17.7 19.8 .89 (0.50,1.58)
2005-2008
15-19 5,626 0 0      
20-24 29,932 53.55 20.55      
25-44 148,465 17.69 18.97      
45-64 34,784 13.84 7.63      
Total 218,807 18.67 16.84 21.5 16.9 1.27 (0.64,2.55)

In each of the 5 year time periods, the standardized rate ratio suggest that having a history of deployment makes one less likely to die from suicide compared to those who do not have a history of deployment. In the time periods 1995 to 1999 and 2000 to 2004, the suicide rate ratios of .89 indicates that the rate of suicide among those male CF members with a history of deployment is 89% of that found among those without a history of deployment. The confidence intervals for both time periods include 1.0 indicating that these findings are not statistically significant. Data from 2005 to 2008 show that there is no statistically significant increase in suicide deaths among those with a history of deployment compared to those without a history of deployment. As with the other time periods, the confidence interval for the rate ratio contains 1.0 signifying that the result is nonsignificant and likely due to chance.

Discussion

The finding that CF suicide rates are lower than the general Canadian population rates is not surprising as CF personnel are a screened, employed population and would be expected to have lower rates of suicide as well as lower rates of other medical problems. Reporting of CF suicides is probably more complete than those of the Canadian population as the latter derive from death certificate records, which are known to under-report suicides. Reporting of CF suicides is a product of both death certificate data as well as records kept by military police.

As shown in Table 1, no recent trend is apparent in CF suicide rates. However due to low numbers and low statistical power, detecting changes in CF suicide rates over time is limited to finding only very gross changes in suicide rates as the numbers are very small.

The SMR analysis comparing the number of observed CF cases to expected cases based on Canadian rates is also limited by the small numbers. Note that if the 95% confidence intervals include 100%, this indicates that if this was considered a sample, chance could not be excluded as a cause for the differences seen from the general Canadian population.

The SMRs comparing the observed number of cases of those with and without a history of deployment with the expected number of cases based on Canadian rates also demonstrate that deployment does not place CF members at high-risk. This is confirmed by the direct standardization rates, which up to 2008 show that there is no statistically significant relationship between history of deployment and risk of suicide.

The annual number of suicides in the CF male population is very small compared to the total CF male population. The value in presenting the 2005 annual data is debatable as a very small change in numbers of suicides results in a large relative change in the SMR estimate. Thus, conclusions drawn from the 2005 SMR analyses must be tentative and take into consideration the instability of the numbers. As future years’ data becomes available, analyses will be conducted using an aggregate year group.

Conclusions

The following conclusions are reached with the understanding that a true difference can be missed due to the small sample size (i.e. the power of the study is low):  

  1. From crude rate of suicide in the Canadian Forces is below those of the general Canadian public, which is not unexpected for a screened, working population.  From 1995 to 2008 there has been no clear change in male CF suicide rates. 
  2. The rate of suicide when standardized for age and sex is lower than that of the general Canadian population.
  3. History of deployment is not a risk factor for suicide in the Canadian Forces.

 


 

1 Rothman KJ, Greenland S. Modern Epidemiology 2nd Edition, Lippincott, Williams, & Wilkins, Philadelphia, 1998, p.260-4.

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