drug-related causes, the contribution to the overall number of deaths was small. The strengths of the study lie in the relatively long followup time after the Vietnam War and, as in the other primary studies reviewed above, the use of multiple databases.

In a retrospective cohort study, Thomas et al. (1991) examined excess mortality in 4582 female veterans who served in Vietnam during the period July 1965-March 1973, and 5324 female veterans who never served in Vietnam. The investigators reported a nonsignificant excess mortality due to external causes, including suicide, in female theater veterans compared with era veterans (RR 1.33, 95% CI 0.80-2.23). There was a significant excess of motor-vehicle accidents (RR 3.19, 95% CI 1.03-9.86). There was no increase in risk of suicide in this cohort of female theater veterans (RR 0.96, 95% CI 0.39-2.39).

Some caution is advisable in using these findings to support a relationship between deployment-related stress and accidental death in that many women deployed to Vietnam were nurses and generally did not witness combat although they were exposed to dead bodies and other traumatic events. However, the investigators estimated cause-specific mortality in the female theater veterans relative to the female era veterans by using a proportional-hazards multivariate model that adjusted for rank (officer or enlisted), military occupation (nursing or other), duration of military service, age at entry into followup, and race. With regard to the nonsignificant finding when suicide alone was used as the outcome, the small number of female veterans who served in Vietnam may not provide sufficient statistical power to detect an association between serving in Vietnam and suicide. Although the study cohort of female Vietnam veterans had sufficient power (95%) to detect an increase in relative risk of death from all causes of 1.3 or greater, the investigators noted that the study had insufficient statistical power to detect moderate increases in deaths from rare causes. Taking the power calculations into consideration may explain why when suicide, accidental death, and nonintentional poisoning are included together as an external cause of death there is sufficient power to detect an increased risk of death in female theater veterans from external causes, especially accidental death, but not suicide.

Bullman and Kang (1996) sought to determine whether there was an association between Vietnam veterans’ exposure to trauma, as indicated by being wounded in combat, and risk of suicide. Subjects were identified from a computerized database, the Casualty Information System, which covered casualties sustained by U.S. Army military and civilian personnel and their dependents worldwide from 1961 to 1981. Of about 70,000 veterans who received nonlethal wounds in 1969-1973, 34,534 were selected randomly for inclusion in the study. Cause-specific mortality in all wounded veterans was compared with that in the U.S. population after adjustment for age, race, and calendar year. In study subjects, there was a slight decrease in overall mortality (standardized mortality ratio 0.97, 95% CI 0.93-1.02). However, study subjects had a statistically significant increase in risk of death from all motor-vehicle accidents (standardized mortality ratio 1.23, 95% CI 1.10-1.37), and all accidents (standardized mortality ratio 1.18, 95% CI 1.09-1.29).

The rate of suicide was slightly, but not significantly, higher in wounded veterans than in U.S. men (standardized mortality ratio 1.12, 95% CI 0.96-1.30). The relative risk of suicide for veterans wounded two or more times compared to those wounded once was 1.50 (95% CI 1.01-2.24). There was a statistically significant increase in risk of suicide in veterans who were wounded more than once and hospitalized for a wound (rate ratio 1.82, 95% CI 1.12-2.96) compared with those wounded once and not hospitalized. In addition, there was a significant trend of increasing risk of suicide with increasing occurrences of combat trauma (χ2 = 5.3, p <



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