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

Toxicology Letters 102]103 Ž1998. 523]526

Epidemiological association in US veterans between Gulf War illness and exposures to anticholinesterases Thomas L. Kurt Department of Internal Medicine, Uni¨ ersity of Texas Southwestern Medical School, PO Box 36032, Dallas, TX 75235, USA

Abstract 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 ŽCB24. men. Extensive surveys were drawn for symptoms and exposures. An existing test ŽPAI. 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 Ž0.82., three major and three minor symptom clusters were identified. Internally consistent by Cronbach’s coefficient, these were labeled syndromes: Ž1. impaired cognition; Ž2. confusion-ataxia; Ž3. arthro-myoneuropathy; Ž4. phobia-apraxia; Ž5. fever-adenopathy; and Ž6. weakness]incontinence. Syndrome variants identified 63 patients Ž63r249, 25%. with 91 syndromes. With pyridostigmine bromide as the drug in these drug-chemical exposures, syndrome chemicals were: Ž1. pesticide-containing flea and tick collars Ž P - 0.001.; Ž2. alarms from chemical weapons attacks Ž P- 0.001., being in a sector later found to have nerve agent exposure Ž P- 0.04.; and Ž3. insect repellent ŽDEET. Ž P- 0.001.. From CB24, 23 cases, 10 deployed and 10 non-deployed controls were studied. Auditory evoked potentials showed dysfunction Ž P- 0.02., nystagmic velocity on rotation testing, asymmetry on saccadic velocity Ž P- 0.04., somatosensory evoked potentials both sides Žright P - 0.03, left P- 0.005. and synstagmic velocity after caloric stimulation bilaterally Ž P-range, 0.02]0.04.. Brain dysfunction was shown on the Halstead Impairment Index Ž P- 0.01., General Neuropsychological Deficit Scale Ž P - 0.03. and Trail Making part B Ž 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. Q 1998 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Cholinesterases; Gulf War; Epidemiology

In April 1994, 3 years after the Persian Gulf War, the National Institutes of Health convened a task force to respond to public outcries that veterans were suffering increasing symptom-associated illness attributed to their wartime exposures ŽNIH Technology Assessment Workshop Panel, 1994.. After my epidemiologic colleague,

Robert Haley, and I participated at that conference in Bethesda, we returned to the University of Texas Southwestern Medical Center at Dallas and formulated plans for human epidemiologic and case-control studies with parallel animal modeling. These were based upon knowing that several potential chemical and drug exposures

0378-4274r98r$ - see front matter Q 1998 Elsevier Science Ireland Ltd. All rights reserved. PII S0378-4274Ž98.00259-8

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T.L. Kurt r Toxicology Letters 102]103 (1998) 523]526

were cholinesterase-inhibiting Žpyridostigmine bromide, chlorpyrifos, nerve agents and cocaine. and overlapped with others that were neurotoxic Žpermethrin, DEET or N, N-diethyl-m-toluamide and chloroquine.; and of the delayed-onset neurotoxic syndrome OPIDP Žorganophosphate-induced delayed polyneuropathy. that can occur ŽAbou-Donia and Lapadula, 1990; Lotti, 1991; Kaplan et al., 1998.. These exposures were built from a list that I initiated as an FDA medical officer at the time of the war. Associated with this was discovered the Army had investigated wearing MOPP chemical protective suits and respirators while exercising in a desert climate chamber, finding this produced heat stress Žhyperthermia. ŽCook and Kolka, 1992; Wenger and Latzka, 1992.. An Israeli group has shown that swimming stress in an animal study lowered the blood]brain barrier ŽBBB. to pyridostigmine bromide ŽPB. ŽFriedman et al., 1966.. Pope and Padilla Ž1990. demonstrated that repeated dosing with PB may have promoted or potentiated neurotoxicity rather than being protective as in the single dose model. And the aged nervous systems of older soldiers appeared more susceptible based upon a similar model ŽHarp et al., 1997.. Our initial epidemiologic project studied 249 members of a Naval Reserve construction battalion ŽCB24. previously reported to have a high rate of Gulf War-attributed symptoms in a limited symptom survey of 50 members. In addition, we tracked down every non-participating member of CB24 to find their age, educational level and rank equivalent comparable to those studies. Two extensive epidemiologic instruments were drawn up, one to survey for symptoms and the other for exposures. Using maps, calendars, illustrations of containers and substances and a decision-tree approach, intricate histories were obtained. The third test instrument was an existing neuropsychologic survey ŽPersonality Assessment Inventory. ŽHaley et al., 1997a.. By using FACTOR, LOGISTIC and FREQ procedures of the 6.07 SAS, a two-stage factor analysis of the symptom data, symptom clusters were sought that had high eigenvalues after rotation. From these orthogonally rotated factor loadings, after Kaiser measure for sampling adequacy

Ž0.82., three major symptom clusters and three minor symptom clusters were identified ŽCattell, 1978; Gorsuch, 1983.. These were internally consistent by Cronbach’s coefficient and labeled Syndrome 1 ‘impaired cognition’, Syndrome 2 ‘confusion-ataxia’, Syndrome 3 ‘arthro-myo-neuropathy’, Syndrome 4 ‘phobia-apraxia’, Syndrome 5 ‘feveradenopathy’ and Syndrome 6 ‘weakness-incontinence’. These syndrome variants identified 63 patients Ž63r249, 25%. with 91 syndromes, 116 Ž116r249, 47%. with serious health problems but no syndromes that could be attributed to Gulf War exposures and 70 Ž70r249, 28%. healthy patients. With all troops at risk taking PB causing combined exposures, risk analysis of the exposure surveys, Syndrome 1 was correlated with the use of pesticide-containing flea and tick collars and pesticide applications in encampments Ž P 0.001., Syndrome 2 with alarms going off from chemical weapons attacks Ž P- 0.001. and being in a certain sector later found to have nerve agent exposure Ž P- 0.04. and Syndrome 3 from heavy use of military supplied insect repellent ŽDEET 75% in ethanol. Ž P- 0.001. ŽHaley and Kurt, 1997.. Twenty-three cases, 10 deployed controls and 10 non-deployed controls from the CB24 were then brought in for extensive neurologic and neuropsychologic evaluations. Auditory evoked potentials demonstrated dysfunction in interside asymmetry of wave I to III Ž P- 0.02., greater interocular asymmetry of nystagmic velocity on rotation testing, increased asymmetric on saccadic velocity Ž P- 0.04., more prolonged interpeak latency of lumbar-to-cerebral peaks of posterior tibial somatosensory evoked potentials on both sides Žright P- 0.03, left P- 0.005. and diminished synstagmic velocity after caloric stimulation bilaterally Ž P-range, 0.02]0.04.. Neuropsychological confirmation showed brain dysfunction on the Halstead Impairment Index Ž P- 0.01., the General Neuropsychological deficit Scale Ž P- 0.03. and on Trail Making part B Ž P- 0.03. ŽHaley et al., 1997b.. These neuropsychologic evaluations have been more extensively described by our colleague, Jim Hom, which discreetly identify syndrome characteristics ŽHom et al., 1997.. Studies of butylcholinesterase phenotypes did not show

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statistical propensity of inherent cholinesterase abnormalities among cases ŽHaley and Kurt, 1997.. Based upon my prior experience of parallel human epidemiologic and animal modeling studies, we considered this approach essential to establish biologic plausibility ŽHoran et al., 1985; Spencer et al., 1985.. Therefore, we sponsored animal modeling studies employing the EPA-hen model for similar combinations of drug-chemical exposures which were implemented at Duke University Medical Center with MB Abou-Donia. These first established sublethal chronic doses of PB, chlorpyrifos, tetrachlorvinphos, DEET, permethrin and chloroquine that could be clinically tolerated. Next, binary and tertiary combinations were administered to look for delayed onset, not acute, neurotoxicity that was confirmed by histologic evaluation of the brain, spinal cord and sciatic nerve ŽAbou-Donia et al., 1996a,b.. Sarin obtained from the DoD was tested similarly confirming that delayed-onset neuropathies can occur with such exposures; and a new method has demonstrated that recent sarin exposure can be biologically documented ŽPolhuijs et al., 1997.. A review of military-sponsored studies at the US Army Institute of Environmental Medicine found that human subjects developed increases in their rectal temperatures Žhyperthermia. while exercising in protective MOPP suits with respirators in a desert climate chamber. Administration of PB impaired ability to adapt under these conditions by decreasing skin capillary flow essential for heat exchange, while niacin had the opposite effect ŽCook and Kolka, 1992; Wenger and Latzka, 1992.. In a parallel animal modeling study in Israel it was shown that PB crosses the blood]brain barrier ŽBBB. in rats subjected to swimming stress ŽFriedman et al., 1966.. These factors strongly suggest that hyperthermic stress might have augmented passage of PB across the BBB either by itself or as a scavenger-carrier of other potentially neurotoxic substances. Another important factor to consider is age from the high rate of Gulf War reported symptoms among mobilized reservists, who were generally 20 years older than regular active duty military. Comparatively this is born out by the low

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rates of Gulf War reported symptoms among studies in the generally younger active duty military and the higher rates in our naval reserve CB24 unit, in addition to other reserve and national guard units studied. By combining highly sophisticated epidemiologic studies with clinical case-control evaluations of identified cases plus parallel animal modeling rendering biologic plausibility, our overall project has uniquely demonstrated the premise that delayed onset neurotoxic variants resulted from stress incubated drug-chemical exposures. Other epidemiologic studies of symptoms have been confirmatory, news reports have described sublethal nerve agent and chemical exposures and neurologic dysfunction has been shown in other case-control reports ŽKiser et al., 1995; Jamal et al., 1996; Amato et al., 1997; The Iowa Persian Gulf Study Group, 1997; Tucker, 1997.. These investigations, taken together, lend credibility that sublethal exposures to combinations of drugs and chemicals in the Gulf War, augmented by hyperthermic stress and age susceptibility, caused the development of delayed-onset neurotoxic syndrome variants. Acknowledgements The author acknowledges the major input of colleagues Robert W. Haley, Jim Hom, and members of the neurologic case-control team at the University of Texas Southwestern, thanks M.B. Abou-Donia at Duke University for his participation and expresses appreciation to the Perot Foundation for support. References Abou-Donia, M.B., Lapadula, D.M., 1990. Mechanisms of organophosphorus ester-induced delayed polyneuropathy. Annu. Rev. Pharmacol. Toxicol. 30, 405]440. Abou-Donia, M.B., Wilmarth, K.W., Jensen, K.F., Oehme, F.W., Kurt, T.L., 1996. Neurotoxicity resulting from coexposure to pyridostigmine bromide, DEET and permethrin. FASEB J. 10, A719; J. Toxicol. Environ. Health 48, 36]56. Abou-Donia, M.B., Wilmarth, K.R., Abdel-Rahman, A.A., Jensen, K.F., Oehme, F.W., Kurt, T.L., 1996. Increased neurotoxicity following simultaneous exposure in pyridostigmine bromide ŽPB., DEET and chlorpyrifos. FASEB J. 10, A1285; Fund. Appl. Toxicol. 34, 201]222.

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