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.
Westberg
M
M
Department of Occupational and Environmental Health, Stockholm Centre for Public Health, Stockholm, Sweden. mattias_westberg@hotmail.com
Feychting
M
M
Jonsson
F
F
Nise
G
G
Gustavsson
P
P
D000328:Adult; D015984:Causality; D002423:Cause of Death; D004784:Environmental Monitoring; D062665:Epidemiological Monitoring; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000209:etiology / Q000401:mortality*; D016273:Occupational Exposure / Q000009:adverse effects* / Q000706:statistics & numerical data*; D012307:Risk Factors; D012959:Socioeconomic Factors; D013548:Sweden / Q000453:epidemiology; D014466:Ultraviolet Rays / Q000009:adverse effects*; D055815:Young Adult