Changes over time in the "healthy soldier effect"

Standardized mortality ratios were used to compare changes in death rates relative to the Australian population in two large studies of Australian servicemen of the Korean War (n = 17,381) and the Vietnam War era (n = 83,908).The healthy soldier effect was most consistently observed in deaths from circulatory diseases. A large deficit in these deaths in the initial follow-up period (10-20 years) was observed before rates tended to rise to the level seen in the general population. There was no healthy soldier effect in deaths from external causes in enlisted personnel, and these death rates were significantly higher than expected in the initial follow-up period among Korean War veterans and regular Army veterans of the Vietnam War. Those selected for national service during the Vietnam War exhibited the strongest healthy soldier effect of all cohorts assessed.Patterns of the healthy soldier effect over time varied markedly by study cohort and by cause of death studied. In a number of analyses, the healthy soldier effect was still apparent after more than 30 years of follow-up.Workers are known to have lower mortality rates than the general population. Good health is necessary to secure and maintain employment, whereas the general population includes sick and disabled people who may be at greater risk of mortality. This observation is known as the "healthy worker effect" and has been frequently reported in occupational epidemiology [1-5].A similar observation in military populations has been termed the "healthy soldier effect" [6-8]. Kang and Bullman proposed that military personnel would have lower mortality than the general population because of initial physical screens, a requirement to maintain a certain standard of physical well-being, and better access to medical care during military service [6]. This healthy soldier effect may result in an underestimation of the effect of an exposure in studies that use the general population as the comparison group.McLaughlin