Suicide and all-cause mortality in Swedish deployed military veterans: a population-based matched cohort study

Objective To investigate suicide and mortality risk in deployed military veterans versus non-deployed comparators who had gone through military conscription testing. Design Population-based matched cohort study. Setting Sweden. Participants Participants were identified from the Military Service Conscription Register and deployment status from the Swedish Military Information Personnel Register. Of 1.9 million conscripts, 21 721 had deployed at some time between 1990 and 2013 (deployed military veterans). Non-deployed comparators were matched to deployed military veterans in two ways: (1) by cognitive ability, psychological assessment, mental health, body mass index, sex, birth-year and conscription-year (carefully matched), with further adjustment for exercise capacity and suicide attempt history; and (2) by sex, birth-year and conscription-year (age- and sex-matched). Main outcome Suicide retrieved from the Swedish National Patient and Causes of Death Register until 31 December 2013. Results During a median follow-up of 12 years, 39 and 211 deaths by suicide occurred in deployed military veterans (n=21 627) and carefully matched non-deployed comparators (n=107 284), respectively (15 vs 16/100 000 person-years; adjusted HR (aHR) 1.07; 95% CI 0.75 to 1.52; p=0.72) and 329 in age- and sex-matched non-deployed comparators (n=108 140; 25/100 000 person-years; aHR 0.59; 95% CI 0.42 to 0.82; p=0.002). There were 284 and 1444 deaths by suicide or attempted suicides in deployed military veterans and carefully matched non-deployed comparators, respectively (109 vs 112; aHR 0.99; 95% CI 0.88 to 1.13; p=0.93) and 2061 in age- and sex-matched non-deployed comparators (158; aHR 0.69; 95% CI 0.61 to 0.79; p<0.001). The corresponding figures for all-cause mortality for carefully matched non-deployed comparators were 159 and 820 (61 vs 63/100 000 person-years; aHR 0.97; 95% CI 0.82 to 1.15; p=0.71) and 1289 for age- and sex-matched non-deployed comparators (98/100 000 person-years; aHR 0.62; 95% CI 0.52 to 0.73; p<0.001). Conclusion Deployed military veterans had similar suicide and mortality risk as non-deployed comparators after accounting for psychological, psychiatric and physical factors. Studies of mental health in deployed veterans need to adjust for more factors than age and sex for comparisons to be meaningful.