Self-reported exposures and their association with unexplained illness in a population-based case-control study of Gulf War veterans.

Many factors have been considered as possible causes of the unexplained illness reported by veterans of the Gulf War (GW). In this study, we report an analysis of risk factors and unexplained illness in a population-based sample of GW veterans who underwent clinical evaluation. Multiple risk factors were compared in 241 veterans who met criteria for unexplained illness and 113 healthy controls. Results suggest that GW unexplained illness is most highly associated with combat conditions, heat stress, and having sought medical attention during the GW. When controlling for multiple simultaneous exposures during the GW, interactions around pyridostigmine bromide, insecticides and repellents, and stress were not significant. These results indicate that most unexplained illness in GW veterans cannot be explained by neurotoxic effects of exposures to chemicals that inhibit cholinesterase activity.