Occupational exposure to UV light and mortality from multiple sclerosis

Background The etiology of multiple sclerosis (MS) is largely unknown; low exposure to ultraviolet (UV) light has been a suggested risk factor. The aim of this study was to investigate whether occupational exposure to UV light reduces the risk of death from MS. Methods The cohort was based on all individuals in the Swedish census in 1980. All MS‐related deaths were identified in the national registry of causes of death. A job‐exposure matrix was developed to classify the occupational exposure to UV light. Results MS was recorded as a cause of the death for 839 individuals. The risk of MS‐related death decreased with increasing occupational exposure to UV light. The relative risk adjusted for age, sex, and socioeconomic status was 0.48 (95% CI 0.28–0.80) in the high‐exposure group and 0.88 (95% CI 0.73–1.06) in the intermediate‐exposure group. Conclusions Occupational exposure to UV light was associated with a reduced risk of MS. Our findings are corroborated by previous observations that UV light has a preventive role in the development of MS, although the possibility of reversed causality cannot be completely ruled out. Am. J. Ind. Med. 52:353–357, 2009. © 2009 Wiley‐Liss, Inc