Multiple sclerosis among utility workers.

The incidence of MS was assessed in a nationwide cohort study of 31,990 employees of Danish utility companies between 1900 and 1993. Overall, 32 cases of MS were diagnosed, as compared with 23.7 expected from national incidence rates, to yield a standardized incidence ratio of 1.35 (95% confidence interval, 0.92 to 1.91). We found no support for the hypothesis of an association between occupational exposure to electromagnetic fields and the risk of MS.