Pooled analysis of all-cause and cause-specific mortality among Nordic military veterans following international deployment

Objectives To investigate all-cause and cause-specific mortality risks, including deaths from external, cardiovascular and cancer causes, among deployed Nordic military veterans in comparison to the general population in each country. Design Pooled analysis. Setting Denmark, Norway, Finland and Sweden. Participants Military veterans deployed between 1990 and 2010 were followed via nationwide registers and compared with age-sex-calendar-year-specific rates in the general population using pooled standardised mortality ratios (SMRs). Main outcomes All-cause and cause-specific mortality retrieved from each country's Causes of Death Register, including deaths from external, cardiovascular and cancer causes. Results Among 83 584 veterans 1152 deaths occurred of which 343 were from external causes (including 203 suicides and 129 traffic/transport accidents), 134 from cardiovascular causes and 297 from neoplasms. Veterans had a lower risk of death from any cause (pooled SMR 0.58, 95% CI 0.52 to 0.64), external causes (0.71, 95% CI 0.64 to 0.79), suicide (0.77, 95% CI 0.67 to 0.89), cardiovascular causes (0.54, 95% CI 0.46 to 0.64) and neoplasms (0.78, 95% CI 0.70 to 0.88). There was no difference regarding traffic/transport accidents for the whole period (1.10, 95% CI 0.92 to 1.31) but the pooled point estimate was elevated, though not statistically significant, during the first 5 years (1.17, 95% CI 0.89 to 1.53) but not thereafter (1.01, 95% CI 0.77 to 1.34). For all other causes of death, except suicide, statistically significantly lower risk among veterans was observed both during the first 5 years and thereafter. For suicide, no difference was observed beyond 5 years. Judged from the country-specific SMR estimates, there was a high degree of consistency although statistically significant heterogeneity was found for all-cause mortality. Conclusions Nordic military veterans had lower overall and cause-specific mortality than the general population for most outcomes, as expected given the predeployment selection process. Though uncommon, fatal traffic/transport accidents were an exception with no difference between deployed military veterans and the general population.