AMYOTROPHIC-LATERAL-SCLEROSIS AND OCCUPATIONAL EXPOSURE TO ELECTROMAGNETIC-FIELDS

In an hypothesis-generating case-control study of amyotrophic lateral sclerosis. lifetime occupational histories were obtained. The patients (n = 28) were clinic based. The occupational exposure of interest in this report is electromagnetic fields (EMFs). This is the first and so far the only exposure analyzed in this study. Occupational exposure u p to 2 years prior to estimated disease symptom onset was used for con struction of exposure indices for cases. Controls (n = 32) were blood and nonblood relatives of cases. Occupational exposure for controls wa s through the same age as exposure for the corresponding cases. Twenty (71%) cases and 28 (88%) controls had at least 20 years of work exper ience covering the exposure period. The occupational history and task data were used to classify blindly each occupation for each subject as having high, medium/high, medium, medium/low, or low EMF exposure, ba sed primarily on data from an earlier and unrelated study designed to obtain occupational EMF exposure information on workers in ''electrica l'' and ''nonelectrical'' jobs, By using the length of time each subje ct spent in each occupation through the exposure period, two indices o f exposure were constructed: total occupational exposure (E(1)) and av erage occupational exposure (E(2)). For cases and controls with at lea st 20 years of work experience, the odds ratio (OR) for exposure at th e 75th percentile of the E(1) case exposure data relative to minimum e xposure was 7.5 (P < 0.02; 95% CI, 1.4-38.1) and the corresponding OR for E(2) was 5.5 (P < 0.02; 95% CI, 1.3-22.5). For all cases and contr ols, the ORs were 2.5 (P < 0.1; 95% CI, 0.9-8.1) for E(1) and 2.3 (P = 0.12; 95% CI, 0.8-6.6) for E(2). This study should be considered an h ypothesis-generating study. Larger studies, using incident cases and i mproved exposure assessment, should be undertaken. (C) 1997 Wiley-Liss , Inc.