Serum Dioxin and Memory Among Veterans of Operation Ranch Hand

摘要

The authors used the Wechsler Memory Scale and the Wechsler Memory Scale-Revised to assess memory among Air Force veterans exposed to Agent Orange and its contaminant, 2,3,7,8-tetrachlor odibenzo-p-dioxin (dioxin), during the Vietnam War. The index subjects were veterans of Operation Ranch Hand, the unit responsible for aerial herbicide spraying in Vietnam from 1962 to 1971. A comparison group of other Air Force veterans who served in Southeast Asia during the same period but were not involved with spraying herbicides, served as referents. Memory was assessed during Air Force Health Study examinations in 1982 and 2002 and dioxin levels were measured in 1987, 1992, 1997, or 2002. The authors 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 they found that the immediate recall portion of the Logical Memory subtest of the Wechsler Memory Scale was decreased among veterans with the highest dioxin exposure in 1982, the results of the study indicate that Agent Orange-exposed Ranch Hand veterans were functioning normally with regards to immediate and delayed memory in 2002. No relation between dioxin exposure and change in memory function between 1982 and 2002 was observed. There does not appear to be any long-term adverse effect with regard to memory functioning. The specific neurological mechanisms (e.g., structural, neurochemical, or other) related to the cause of the 1982 deficits in memory are unknown; however, these changes likely have been reversed.