Epidemiological association in US veterans between Gulf War illness and exposures to anticholinesterases

To investigate complaints of Gulf War veterans, epidemiologic, case-control and animal modeling studies were performed. Looking for OPIDP variants, our epidemiologic project studied 249 Naval Reserve construction battalion (CB24) men. Extensive surveys were drawn for symptoms and exposures. An existing test (PAI) was used for neuropsychologic. Using FACTOR, LOGISTIC and FREQ in 6.07 SAS, symptom clusters were sought with high eigenvalues from orthogonally rotated two-stage factor analysis. After factor loadings and Kaiser measure for sampling adequacy (0.82), three major and three minor symptom clusters were identified. Internally consistent by Cronbach's coefficient, these were labeled syndromes: (1) impaired cognition; (2) confusion-ataxia; (3) arthro-myo-neuropathy; (4) phobia-apraxia; (5) fever-adenopathy; and (6) weakness-incontinence. Syndrome variants identified 63 patients (63/249, 25%) with 91 syndromes. With pyridostigmine bromide as the drug in these drug-chemical exposures, syndrome chemicals were: (1) pesticide-containing flea and tick collars (P < 0.001); (2) alarms from chemical weapons attacks (P < 0.001), being in a sector later found to have nerve agent exposure (P < 0.04); and (3) insect repellent (DEET) (P < 0.001). From CB24, 23 cases, 10 deployed and 10 non-deployed controls were studied. Auditory evoked potentials showed dysfunction (P < 0.02), nystagmic velocity on rotation testing, asymmetry on saccadic velocity (P < 0.04), somatosensory evoked potentials both sides (right P < 0.03, left P < 0.005) and synstagmic velocity after caloric stimulation bilaterally (P-range, 0.02-0.04). Brain dysfunction was shown on the Halstead Impairment Index (P < 0.01), General Neuropsychological Deficit Scale (P < 0.03) and Trail Making part B (P < 0.03). Butylcholinesterase phenotypes did not trend for inherent abnormalities. Parallel hen studies at Duke University established similar drug-chemical delayed neurotoxicity. These investigations lend credibility that sublethal exposures to drug-chemical combinations caused delayed-onset neurotoxic variants.