active duty (1965) and ended at death or on December 31, 1983, whichever came first, the total death rate of theater veterans was 17% higher than that of era veterans, and theater veterans had a 25% higher mortality due to external causes. The excess mortality during the early followup period (considered to be the first 5 years) was due largely to external causes (rate ratio 1.25, 95% CI 1.00-1.55), including motor-vehicle accident (rate ratio 1.93, 95% CI 1.16-3.22), suicide (rate ratio 1.72, 95% CI 0.76-3.88), homicide (rate ratio 1.52, 95% CI 0.59-3.91), and accidental poisoning (rate ratio 1.69, 95% CI 0.49-5.77); the death rate ratio for all causes of death was 1.45 (95% CI 1.08-1.96) for the first 5 years after discharge and 1.01 (95% CI 0.79-1.28) after 6 or more years. Death from motor-vehicle crashes was almost 2 times more likely in theater veterans than in era veterans during the early followup period. Alcohol use did not appear to account for the excess risk of a fatal motor-vehicle crash. A similar increase in risk was found for suicide during the early followup period; adjustment for covariates increased the risk ratio for suicide in the early followup period from 1.7 (95% CI 0.76-3.88) to 2.59 (95% CI 1.09-6.17) based on death certificates analyses and to 2.56 (95% CI 1.11-5.87) based on medical review panel assessment. Thereafter, the ratio for suicide declined until it was no more than 1.0. The rate ratios for homicide and other accidents also were below 1.0 in the later followup period and the rate ratio for motor vehicle accidents was 1.16 (95% CI 0.72-1.87).

Boehmer et al. (2004) studied postservice mortality in a 30-year followup of Vietnam veterans by obtaining data on vital status and underlying causes of death on 18,313 male U.S. Army veterans in the VES cohort, thus extending followup an additional 17 years. Vital status was retrospectively ascertained from the end of the original study (1984) through 2000 by using three national databases: the VA BIRLS, the Social Security Administration’s Death Master File, and the National Death Index Plus. Potential matches from each data source were reviewed manually, and underlying cause-of-death codes were obtained from the National Death Index Plus. If data on cause of death were not available from the National Death Index Plus, official copies of death certificates were obtained, and an experienced nosologist at National Center for Health Statistics (NCHS) coded the cause of death. NCHS converted ICD-9 and ICD-10 causes of death to the NCHS list of 113 selected causes of death, which were then categorized for external causes to allow comparisons with the original study.

Crude death rates were calculated separately for Vietnam-theater and Vietnam-era veterans by using person-years at risk, beginning with the day of discharge from service and ending with the date of death or December 31, 2000, whichever came first. Cox proportional-hazards models were used to approximate the adjusted relative risks for all-causes mortality; for each model, potential confounding and effect modification were assessed. Standardized mortality ratios were used to compare veteran death rates with those in the U.S. male population; they were adjusted for age, race, and calendar year but were limited to deaths through 1998 because U.S. rates had not yet incorporated ICD-10 codes when the analysis was conducted. There were 1138 new deaths during the additional followup period, five of which occurred during the previous study but had not been identified then. At 5 years since discharge, the only significant external cause of death was accidental poisoning (rate ratio 2.58, 95% CI 1.09-6.14). Mortality due to motor-vehicle accidents or suicide was not significantly higher in theater veterans than in era veterans more than 5 years after discharge from the service (rate ratio 1.02, 95% CI 0.73-1.43 and rate ratio 0.93, 95% CI 0.64-1.34, respectively). However, there continued to be an excess of drug-related deaths among Vietnam veterans during the entire followup period, and there was some overlap between the definitions of unintentional poisoning and drug-related death. The authors noted that even though theater veterans were more likely than era veterans to die from

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