The new study, the first to compare the brain-related and psychological functions of ill and well veterans, found no evidence of psychological problems, including post-traumatic stress disorder or other stress-related illnesses.
Results are published in the August Archives of Clinical Neuropsychology.
The analysis shows ill veterans from a U.S. Navy reserve unit consistently performed worse than healthy veterans from the same battalion in an exhaustive, day-long battery of neuropsychological tests conducted by Dr. Jim Hom at The Neuropsychology Center in Dallas. He was "blinded" to the veterans' status, unaware which were ill until after the test results were analyzed.
"We comprehensively tested a broad range of brain-related function," said Hom, a clinical assistant professor of neurology at UT Southwestern. "The ill veterans performed worse on 59 of the 71 brain-related measures. Their psychological profile was similar to profiles of individuals with general medical problems and did not include psychopathology. Clearly, the ill veterans demonstrated a neuropsychological pattern of impairment that is indicative of generalized brain damage, not psychological reactions."
The study is part of the ongoing investigation at UT Southwestern into the illnesses reported by as many as 70,000 Gulf War veterans. It bolsters the researchers' conclusion, published in the Jan. 15 Journal of the American Medical Association, that some veterans are suffering from brain and nerve damage linked to their wartime use of flea collars, insect repellent and anti-nerve gas pills, as well as exposure to chemical nerve agents.
With a series of blinded epidemiological and clinical studies on veterans of the 24th Naval Mobile Construction Battalion, the UT Southwestern researchers identified a syndrome characterized by thought, memory and sleep difficulties; a second syndrome that involves more severe thought problems as well as confusion and imbalance; and a third syndrome of sore joints and muscles and tingling or numbness of the hands and feet. The syndromes are variants of a rare disorder called organophosphate-induced delayed polyneuropathy, which is caused by exposure to certain chemicals that inhibit cholinesterase, an enzyme important to nervous system function.
For this study, to assess the cognitive and psychological function of 26 veterans with the newly identified syndromes (the "cases") and 20 healthy veterans (the "controls" -- half of whom went to the Gulf War), Hom put each through a series of standard neuropsychological tests used to assess the extent of damage caused by brain injury and disease. The researchers said the cases' pattern of deficits in intelligence, problem-solving, attention and concentration, memory and learning, language, sensorimotor abilities and other brain functions is strikingly similar to those reported in a 1988 study of workers poisoned by organophosphate poisons in the work place.
"This study supports our overall theory that the syndromes we identified represent neurological damage from combinations of chemicals," said Dr. Robert Haley, who heads UT Southwestern's Gulf War syndrome research and is chief of epidemiology. "We developed the first case definition of Gulf War syndrome and this shows that our case definition is a marker for brain injury."
Haley, Hom and toxicologist Dr. Tom Kurt of the clinical faculty were the UT Southwestern researchers involved in this phase of UT Southwestern's ongoing search for a way of testing for the syndromes and eventually treating them.
Last year the UT Southwestern team, working in collaboration with researchers at Duke University Medical Center, reported that combinations of DEET in insect repellent, chlorpyrifos (Dursban) in flea collars and the anti-nerve gas pills containing pyridostigmine bromide caused neurotoxicity in hens when given in two- or three-way combinations but not when given individually.
The Perot Foundation provided funding for the studies.
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