Article

The Air Force Health Study: An Epidemiologic Retrospective

School of Public Health, Division of Epidemiology, University of California, Berkeley, Berkeley, CA 94720, USA.
Annals of epidemiology (Impact Factor: 2). 03/2011; 21(9):673-87. DOI: 10.1016/j.annepidem.2011.02.001
Source: PubMed

ABSTRACT

In 1979, the U.S. Air Force announced that an epidemiologic study would be undertaken to determine whether the Air Force personnel involved in Operation Ranch Hand-the program responsible for herbicide spraying in Vietnam-had experienced adverse health effects as a result of that service. In January 1982 the Air Force Health Study (AFHS) protocol was approved and the 20 year matched cohort study consisting of independent mortality, morbidity and reproductive health components was initiated. This controversial study has been criticized regarding the study's potential scientific limitations as well as some of the administrative aspects of its conduct. Now, almost 30 years since the implementation of the AFHS and nearly a decade since the final follow up examinations, an appraisal of the study indicates that the results of the AFHS do not provide evidence of disease in the Ranch Hand veterans caused by their elevated levels of exposure to Agent Orange.

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    • "The highest values were found in the maintenance personnel who came into direct contact with the liquid herbicide, and who were responsible for loading the herbicide into the planes, cleaning the spray equipment and repairing the aircraft[37]. During the six examinations conducted over the 20 years, the AFHS investigated over 300 health endpoints on multiple occasions.[37]. The long history of safe use of 2,4,5-T containing a thousand or more times as much TCDD as was present in the 1970s (0.01 ppm) must be recognized. "
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    ABSTRACT: A dose-response relationship between serum 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) and adult diabetes risk has been reported among U.S. Vietnam veterans in the Ranch Hand (RH) cohort. We examine the hypothesis that diabetes progression leads to higher serum dioxin (reverse causation) rather than higher serum dioxin leading to diabetes (causation) across the longitudinal medical monitoring data on these airmen. Lipid-adjusted serum dioxin levels and clinical parameters relating to diabetes progression were examined. Potential confounding due to age, race, diabetes family history, serum total lipid, and body mass index (BMI) was accounted for. The similar incidence of diabetes in RH and Comparison veterans, along with generally similar incidence trends with dioxin decile and lipid decile despite the large differential in serum dioxin, is evidence consistent with reverse causation. Of 135 RH diabetics with at least two dioxin measurements, 32.6% had a temporary serum dioxin increase more than a decade after Vietnam tour and another 22.2% had an interval of unusually slow half-life (>15.5 years); these diabetes-related changes shifted more diabetics into the higher dioxin deciles. Further, the increased diabetes odds ratio among the generally younger RH veterans in the highest dioxin decile is associated with a higher incidence of adult obesity in this RH subgroup, both at tour of duty and decades later. Change in serum dioxin levels is likely due to diabetes progression or poor control and is not independently related to serum dioxin concentrations. In summary, the data from the Ranch Hand studies does not indicate that dioxin increases adult diabetes risk.
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