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Evidence for Excess Rates of Birth Defects in Gulf War Veterans from Reanalysis of Findings from Federally Sponsored Studies

Robert W. Haley, M.D.

Epidemiology Division, Department of Internal Medicine,
University of Texas Southwestern Medical Center, Dallas, Texas

Two Federally sponsored studies of birth defects compared rates of birth defects in all 695,000 Gulf War veterans with rates in a 50% random sample of the non-deployed era veterans. Tests of statistical significance were calculated assuming that the groups represented random samples from an infinite population, or a "super-population" Since the conditions to which Gulf War veterans were exposed in the war were unique and a primary purpose of the studies was to determine whether Gulf War veterans are to be compensated for illnesses and birth defects, the populations must be treated as finite populations, at least for settling the question of compensation. Consequently, estimates of variance for risk measures must be adjusted for the probability of selection. Since all members of the deployed group were studied, the risks of birth defects measured in this group are known exactly, with no sampling error, and since a 50% random sample of the non-deployed were studied, the risks in this group are known with only 30% of the usual sampling error. Cowan et al. found the relative risk of congenital hip dysplasia associated with deployment to be 1.31 in the offspring of the men and 1.38 in those of the women. The authors, assuming a super-population model, reported both relative risks as not statistically significant, with 95% confidence intervals (CI) of 0.94-1.83 for the men and 0.67-1.81 (sic) for the women. After adjusting for the finite population correction, both relative risks were statistically significant (95% CI 1.10-1.56 for the men and 1.01-1.88 for the women). With the effect being homogeneous across gender (p=.9 by Wolfe's test for homogeneity), the combined relative risk was right at statistical significance even without adjusting for the finite population correction (Mantel-Haenszel [MH] RR 1.32, 95% CI 0.98-1.79; MH X2=3.24, df=1, p=.07) and highly statistically significant after adjusting for the finite population correction (MHfpc RR 1.32, 95% CI 1.15-1.51; MHfpc X2=16.11, df=1, p=.00006). Given that the authors tested for the effects of war exposure on the six most common birth defects in the men and the seven most common in the women (32), for a result to be statistically significant despite the multiple hypothesis testing one might require its p value to be below the most conservative Bonferroni-adjusted value of p=.0038 (.05/13), and it remains statistically significant by this criterion. Araneta et al. reported a 3-fold higher risk of Goldenhar syndrome to be non-significant (RR 3.03; 95% CI 0.63-20.57); however, when adjusted for the finite population correction it is statistically significant (RRfpc 3.03, 95% CI 1.14-8.08). Given that ill Gulf War veterans disproportionately left the military soon after the war and their offspring were selectively lost to followup by the surveillance confined to military hospitals, the excess risks of birth defects were underestimated. I conclude that offspring of the deployed veterans had higher risks of some birth defects than those of the non-deployed.

Meta-Analysis; Birth Defects; Finite Population Correction

No support but findings relevant to Federally supported Gulf War veterans’ illnesses research

Return to Epidemiology

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