Olfactory and Cognitive Decrements in 1991 Gulf War Veterans

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Abstract
Background Prominent symptoms of Gulf War illness (GWI), the disorder related to military service in the 1991 Gulf War (GW), include fatigue, pain, and cognitive dysfunction. Although anosmia is not a typical GWI symptom, anecdotally some veterans reported losing their sense smell shortly after the war. Because olfactory deficit is a prodromal symptom of neurodegenerative diseases like Parkinson’s and Alzheimer’s disease, and because we previously reported suggestive evidence that deployed GW veterans may be at increased risk for Mild Cognitive Impairment (MCI) and dementia, the current study examined the relationship between olfactory and cognitive function in deployed GW veterans. Methods Eighty deployed GW veterans (mean age: 59.9 ± 7.0; 4 female) were tested remotely with the University of Pennsylvania Smell Identification Test (UPSIT) and the Montreal Cognitive Assessment (MoCA). Veterans also completed self-report questionnaires about their health and deployment-related exposures and experiences. UPSIT and MoCA data from age-matched healthy controls (HC) were downloaded from the Parkinson’s Progression Markers Initiative (PPMI) study for comparison. Results GW veterans had a mean UPSIT score of 27.8 ± 6.3 (range 9–37) and a mean MoCA score of 25.3 ± 2.8 (range 19–30). According to age- and sex-specific normative data, 31% of GW veterans (vs. 8% PPMI HCs) had UPSIT scores below the 10th percentile. Nearly half (45%) of GW veterans (vs. 8% PPMI HCs) had MoCA scores below the cut-off for identifying MCI. Among GW veterans, but not PPMI HCs, there was a positive correlation between UPSIT and MoCA scores (Spearman’s ρ = 0.39, p < 0.001). There was no significant difference in UPSIT or MoCA scores between GW veterans with and without history of COVID and with and without Kansas GWI exclusionary conditions. Conclusions We found evidence of olfactory and cognitive deficits and a significant correlation between UPSIT and MoCA scores in a cohort of 80 deployed GW veterans. Because impaired olfactory function has been associated with increased risk for MCI and dementia, it may be prudent to screen aging, deployed GW veterans with smell identification tests so that hypo- and anosmic veterans can be followed longitudinally and offered targeted neuroprotective therapies as they become available.

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