25 Longitudinal Decline in Memory in 1991 Gulf War Veterans: Where you Start Matters.

Abstract

Objective:Memory complaints have been a concern of Gulf War (GW) veterans since their return from the war in 1991, and over time it has been reported that exposures to neurotoxicants during the war have been associated with memory decline from premorbid levels. However, many of the studies that have shown slight or no memory decrements only looked at one time point and have not followed participants to document trajectory of symptoms over time. Longitudinal design is an optimal way to document change in cognitive function over time and the Fort Devens cohort (FDC), the longest running cohort of GW veterans, is ideal for assessing such change. This prospectively designed non-treatment seeking cohort were assessed at multiple timepoints with neuropsychological assessments and surveys. Initial neuropsychological assessments from 1997 showed above average scores on tests of verbal memory (California Verbal Learning Test) and average nonverbal memory (Wechsler Memory Scale-R) performances. A follow-up study of neuropsychological testing was completed between 2019-2022. This study was designed to document change in cognitive status between the two time points.Participants and Methods:Participants (N=50) from the original 1991 cohort were again tested from 2019-2022. Neuropsychological tests included California Verbal Learning Test-Second edition (CVLT2) for verbal learning, and the visual reproduction subtest from the Wechsler Memory Scale-Revised (WMS-R) for nonverbal learning and memory. For both time points, the average scores of the participants were compared with age scaled scores for each neuropsychological test.Results:The mean age of our current participants was 58 years. 72% were men. Relative to standardized test norms at the first time point, the scores for total learning from trials 1 through 5 from the CVLT2 were in the above average range relative to age and gender-based norms. During the second time point, the participants average scores on the same scale had dropped to the average range, one full standard deviation below their prior performances. In addition, at the first time point, total learning from visual reproductions was in the average range and dropped to the low average range for the second time point. This value dropped by one-half a standard deviation.Conclusions:Results showed significant diminishment in verbal and visual memory relative to prior test performances. Whenever possible, documenting the trajectory of symptoms relative to where each participant started on neuropsychological functional outcomes is key to understanding the longitudinal impact of neurotoxicant and other war-related exposures in military veterans. Given this decline, further assessment of GW veterans’ cognitive trajectories is warranted.