Secondary Studies

Two secondary studies that assessed the association of diabetes with having served in Vietnam were identified. Eisen et al. (1991) used the Vietnam Era [1965-1975] Twin Registry of male-male (monozygotic and dizygotic) twins born in 1939-1957 to assess the prevalence of self-reported diabetes in 2260 pairs of male monozygotic twins who were discordant for the disease. Twins were surveyed by mail or telephone interview in 1987 and asked whether they had ever had diabetes (or 12 other health conditions). Of the twins with and without current diabetes, 50% and 55%, respectively, had served in Southeast Asia for an insignificant OR of 0.8 (95% CI 0.2-3.4). When twins were surveyed as to whether they had ever had diabetes since service in Southeast Asia (as opposed to currently having diabetes), there was still an insignificant OR of 3.0 (95% CI 0.6-14.9), indicating that service in Vietnam was not associated with an increased frequency of diabetes. The study had a high response rate, 74.4%, but is limited by the lack of a physical examination to confirm the presence of diabetes.

In the only study that attempted to associate self-reports of diabetes with combat stress, O’Toole et al. (1996b) found that the risk of diabetes did not appear to be linked to increasing combat exposure in Australian Vietnam veterans. A random sample of 641 Australian Army veterans posted to Vietnam in 1964-1972 was interviewed with a health survey questionnaire and a combat-exposure index 20-25 years after the war. Combat-exposure responses were divided into severity quartiles. The ORs for diabetes compared with combat exposure were 1.00, 0.56, 0.92, and 0.61 for each quartile of increase in combat score (p = 0.557); the lowest score quartile was used as the referent.

Five secondary studies looked at the presence of diabetes among Gulf War veterans, on the basis of self-reports, and found no significant increase in the prevalence of diabetes in Gulf War veterans compared with their nondeployed counterparts. Gray et al. (2002) surveyed members of the U.S. Naval Mobile Construction Battalions (Seabees) in 1997-1999 by mail questionnaire about medical conditions for which they had received a physician’s diagnosis. Seabees deployed to the gulf region (n = 3831) were compared with Seabees deployed elsewhere (n = 4933) and not deployed (n = 3104). Diabetes mellitus was reported by 1.04% of Gulf War-deployed Seabees, 0.91% of those deployed elsewhere, and 1.61% of nondeployed Seabees. The OR for having a diagnosis of diabetes among Gulf War Seabees compared with nondeployed Seabees was 0.77 (95% CI 0.49-1.23) adjusted for age, sex, active-duty or reserve status, race and ethnicity, current smoking, and current alcohol drinking.

Similar results were seen by McCauley et al. (2002b), who conducted a telephone survey of Gulf War veterans from Oregon, Washington, California, North Carolina, and Georgia to assess the prevalence of self-reported medical conditions or hospitalizations 9 years after the war. Veterans were categorized as having been within 50 miles of the Khamisiyah munitions bunker in Iraq (n = 653) with possible exposure to chemical-warfare agents, in the Gulf War region but not in the Khamisiyah area (n = 610), and not deployed to the gulf region (n = 516). The frequency of self-reported diagnoses of diabetes with onset after Gulf War service was 2.3% in all deployed veterans, whether or not they were near Khamisiyah, and 2.5% in nondeployed veterans for a nonsignificant OR of 1.0 (95% CI 0.5-2.4) adjusted for age, sex, race, and region of residence.

In 1998, Steele (2000) assessed the prevalence of self-reports of physician-diagnosed or treated diabetes in 1548 Gulf War-deployed veterans and 482 veterans who served elsewhere. All veterans were living in Kansas at the time of the telephone survey; disease onset must have occurred during 1990-1998. The incidence of diagnosis in this time period was 1% in both



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