Serum dioxin and cognitive functioning among veterans of Operation Ranch Hand

We used the Halstead-Reitan neuropsychological test battery, the Wechsler a dult intelligence scale-revised, the Wechsler memory scale, and the wide ra nge achievement test to assess cognitive functioning among Air Force vetera ns exposed to Agent Orange and its contaminant, 2,3,7,8-tetrachlorodibenzo- p-dioxin (dioxin), during the Vietnam war The index subjects were veterans of Operation Ranch Hand (N = 937), the unit responsible for aerial herbicid e spraying in Vietnam from 1962 to 1971. A comparison group of other Air Fo rce veterans (N = 1052), who served in Southeast Asia during the same perio d but were not involved with spraying herbicides served as referents. Cogni tive functioning was assessed in 1982, and dioxin levels were measured in 1 987 and 1992. We assigned each Ranch Hand veteran to the background, low, o r high dioxin exposure category on the basis of a measurement of dioxin bod y burden. Although we found no global effect of dioxin exposure on cognitiv e functioning, we did find that several measures of memory functioning were decreased among veterans with the highest dioxin exposure.. These results became more distinct when we restricted the analysis to enlisted personnel, the subgroup with the highest dioxin levels. An analysis based on dioxin q uintiles in the combined cohort produced consistent results, with veterans in the fifth quintile exhibiting reduced verbal memory function. Although s tatistically significant, these differences were relatively small and of un certain clinical significance. Published by Elsevier Science Inc.