across demyelinated nerves when the core body temperature is raised. Second, a variety of infections can increase the risk of MS attacks, and it is well established that soldiers in both the Gulf War and in the conflicts in Iraq and Afghanistan experienced numerous infectious illnesses (see IOM, 2007). A third potential deployment-related risk is that of multiple vaccinations; however, there is no convincing evidence that any vaccinations are risk factors for MS (reviewed in Compston, 2006). Finally, it is possible that psychological and physical stress associated with war might increase MS risk, as has been recently reported from Israel (Golan et al., 2008).
There was no information related to MS at the time of the last IOM review in 2006. Barth et al. (2009) reviewed mortality from MS as well as from ALS, Parkinson’s disease, and brain cancer from 621,902 veterans who served in the Gulf War between August 1, 1990, and March 1, 1991, and compared these with 746,248 veterans who served concurrently but were not deployed to the gulf. Follow-up was terminated on December 31, 2004. Records from the VA database Beneficiary Identification and Records Locator Subsystem (BIRLS), a file consisting of all veterans eligible for VA benefits, and the SSA Death Masterfile were examined. Death certificates and medical records were reviewed by experts who were blinded to deployment status and classified using the McDonald criteria (McDonald et al., 2001). A total of 19 deaths due to MS were identified; 6 in the deployed group and 13 nondeployed. The adjusted relative risk estimates for MS mortality did not suggest an increased risk of mortality from MS (RR 0.67, 95% CI 0.24-1.85; Cox proportionate hazard model).
Kelsall et al. (2005) performed a cross-sectional analysis of the entire cohort of 1871 Australian Gulf War veterans, and a comparison group of 2924 nondeployed veterans, matched by age, sex and service type. Postal and telephone questionnaires were administered followed by evaluations at 10 clinics across country. MS was self-identified in one Gulf War veteran and in three in the comparison group (OR 0.3, 95% CI 0.00-3.5). Because of the small size and limitations of this study, and the fact that MS was determined by self-report, no conclusions can be drawn about the prevalence of MS in this cohort; therefore, this study is considered to be secondary for this health outcome.
No excess in MS mortality was identified in Gulf War veterans in a single well-executed primary study. However, for several reasons the design of the study is likely to be insensitive to the detection of any MS risk associated with deployment. First, the study could detect deaths from MS within 13 years or less from the time of deployment, yet epidemiologic data suggest that the interval between a critical environmental exposure and the clinical onset of MS may be a decade or longer. Second, any excess mortality due to MS is likely to be only minimal during the first 15 years of the illness. Thus a mortality endpoint with a short duration study is unlikely to have power to detect an increase in the occurrence of clinical MS among those deployed in the 1990-1991 conflict.