A new study finds that Gulf War veterans who had low-level exposure to chemical weapons are likely to experience long-term negative effects on brain structure and memory function.
In previous research, Linda Chao, Ph.D., and colleagues of San Francisco VA Medical Center reported decreased volume of the hippocampus — a brain area involved in memory processing — in Gulf War veterans who had been exposed to the Khamisiyah plume.
Khamisiyah is an area in southern Iraq approximately 217 miles southeast of Baghdad. In 1991, demolition of an Iraqi munitions depot in that area caused U.S. soldiers to be exposed to low levels of nerve agents, carried downwind in a smoke plume.
While the previous research had some limitations, including a lack of data on other risk factors, the new study compared an independent group of 113 veterans with predicted exposure to the Khamisiyah plume, based on Department of Defense models, and 62 non-exposed veterans.
Using brain magnetic resonance imaging, the researchers found that the hippocampus was significantly smaller in veterans with predicted exposure. The difference remained significant even after accounting for a wide range of other factors, including meeting criteria for Gulf War illness, the presence of an Alzheimer’s disease risk gene (ApoE4), brain injury or depression.
Among veterans with predicted exposure to the Khamisiyah plume, smaller hippocampus volume was associated with lower scores on a test of verbal learning and memory. Scores on the memory test were also lower for veterans with higher estimated exposure and for those with self-reported memory difficulties.
The discovery that these effects are still present 25 years later, after adjusting for potential confounding factors, supports the notion that exposure to the Khamisiyah plume has lasting adverse effects on Gulf War veterans.
Since memory problems and smaller hippocampal volumes have both been linked to the risk of late life dementia, Chao and colleagues believe that veterans who were exposed to the Khamisiyah plume should receive regular follow-up checkups, especially as they approach old age.
Many Gulf War veterans are affected by a condition known as “chronic multisymptom illness,” a cluster of medically unexplained chronic symptoms that can include fatigue, headaches, joint pain, indigestion, insomnia, dizziness, respiratory disorders, and memory problems.
The new findings are published in the October Journal of Occupational and Environmental Medicine.