Serum dioxin and cognitive functioning among veterans of Operation Ranch Hand

Joel E. Michalek, Fatema Z. Akhtar, Joseph C. Arezzo, David H. Garabrant, James W. Albers

    Research output: Contribution to journalArticlepeer-review

    35 Scopus citations


    We used the Halstead-Reitan neuropsychological test battery, the Wechsler adult intelligence scale-revised, the Wechsler memory scale, and the wide range achievement test to assess cognitive functioning among Air Force veterans 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 herbicide spraying in Vietnam from 1962 to 1971. A comparison group of other Air Force veterans (N = 1052), who served in Southeast Asia during the same period but were not involved with spraying herbicides served as referents. Cognitive functioning was assessed in 1982, and dioxin levels were measured in 1987 and 1992. We assigned each Ranch Hand veteran to the background, low, or high dioxin exposure category on the basis of a measurement of dioxin body burden. Although we found no global effect of dioxin exposure on cognitive 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 quintiles in the combined cohort produced consistent results, with veterans in the fifth quintile exhibiting reduced verbal memory function. Although statistically significant, these differences were relatively small and of uncertain clinical significance.

    Original languageEnglish (US)
    Pages (from-to)491-502
    Number of pages12
    Issue number4
    StatePublished - 2001


    • Cognitive function
    • Dioxin
    • Epidemiology
    • Herbicide
    • Memory
    • TCDD

    ASJC Scopus subject areas

    • General Neuroscience
    • Toxicology


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