Associations between the self-reported frequency of hearing chemical alarms in theater and regional brain volume in Gulf War Veterans

Abstract

Background We previously reported evidence of reduced cortical gray matter (GM), white matter (WM), and hippocampal volume in Gulf War (GW) veterans with predicted exposure to low-levels of nerve agent according to the 2000 Khamisiyah plume model analysis. Because there is suggestive evidence that other nerve agent exposures may have occurred during the Gulf War, we examined the association between the self-reported frequency of hearing chemical alarms sound during deployment in the Gulf War and regional brain volume in GW veterans. Methods Ninety consecutive GW veterans (15 female, mean age: 52±8 years) participating in a VA-funded study underwent structural magnetic resonance imaging (MRI) on a 3 T scanner. Freesurfer (version 5.1) was used to obtain regional measures of cortical GM, WM, hippocampal, and insula volume. Multiple linear regression was used to determine the association between the self-reported frequencies of hearing chemical alarms during the Gulf War and regional brain volume. Results There was an inverse association between the self-reported frequency of hearing chemical alarms sound and total cortical GM (adjusted p = 0.007), even after accounting for potentially confounding demographic and clinical variables, the veterans’ current health status, and other concurrent deployment-related exposures that were correlated with hearing chemical alarms. Post-hoc analyses extended the inverse relationship between the frequency of hearing chemical alarms to GM volume in the frontal (adjusted p = 0.02), parietal (adjusted p = 0.01), and occipital (adjusted p = 0.001) lobes. In contrast, regional brain volumes were not significantly associated with predicted exposure to the Khamisiyah plume or with Gulf War Illness status defined by the Kansas or Centers for Disease Control and Prevention criteria. Conclusions Many veterans reported hearing chemical alarms sound during the Gulf War. The current findings suggest that exposure to substances that triggered those chemical alarms during the Gulf War likely had adverse neuroanatomical effects.

Neuropsychological characteristics of Gulf War illness: A meta-analysis

“…These results are similar to exposure-outcome decrements recently noted in meta-analyses of OP and carbamate occupationally exposed pesticide applicators and agricultural workers[34, 35, 39]. Collectively, these results indicate chronic cognitive effects from neurotoxicant exposures that would be expected given the functional correlates of neuroimaging findings in exposed GW populations (lower cortical, hippocampal and white matter volumes in exposed groups) [26, 27, 37, 38, 40]. Researchers in the field of GWI have called for a better-refined case definition of the disorder[1].…”

The Prevalence of Mild Cognitive Impairment in a Convenience Sample of 202 Gulf War Veterans

“…Demographic and descriptive characteristics were compared across three cognitive groups with analysis of variance (ANOVA) for continuous variables and chi-square tests for categorical variables. Because we previously reported significant effects of predicted exposure to the Khamisiyah plume on hippocampal and total cortical gray matter volumes [ 56 , 57 , 58 ], Khamisiyah exposure status was included as a covariate in analyses of the hippocampal volume and measures of cortical thickness. We also accounted for apolipoprotein E (APOE) genotype in analyses of hippocampal volume and cortical thickness.…”

The Multiple Hit Hypothesis for Gulf War Illness: Self-Reported Chemical/Biological Weapons Exposure and Mild Traumatic Brain Injury

“…It has been found in numerous studies that GW veterans with exposure to neurotoxicants, including pesticides, pyridostigmine bromide pills, and chemical/biological weapons (CBW), have higher rates of chronic symptoms than those without such exposures [ 6 ]. In fact, a recent study found a strong inverse correlation with veterans reporting total number of chemical alarm sounds heard during the war and total cortical gray matter brain volumes [ 7 ]. Additionally, GW veterans with an increased reporting of CBW exposures have more frequently met criteria for the current GW Illness case definitions [ 8 ], including chronic multi-symptom illness (CMI) [ 9 ] and Kansas GWI criteria [ 10 ], than those without such exposures [ 11 , 12 , 13 ].…”