Objective: To examine whether past high sun exposure is associated with a reduced risk of multiple sclerosis. Design: Population based case-control study. Setting: Tasmania, latitudes 41-3°S. Participants: 136 cases with multiple sclerosis and 272 controls randomly drawn from the community and matched on sex and year of birth. Main outcome measure: Multiple sclerosis defined by both clinical and magnetic resonance imaging criteria. Results: Higher sun exposure when aged 6-15 years (average 2-3 hours or more a day in summer during weekends and holidays) was associated with a decreased risk of multiple sclerosis (adjusted odds ratio 0.31, 95% confidence interval 0.16 to 0.59). Higher exposure in winter seemed more important than higher exposure in summer. Greater actinic damage was also independently associated with a decreased risk of multiple sclerosis (0.32, 0.11 to 0.88 for grades 4-6 disease). A dose-response relation was observed between multiple sclerosis and decreasing sun exposure when aged 6-15 years and with actinic damage. Conclusion: Higher sun exposure during childhood and early adolescence is associated with a reduced risk of multiple sclerosis. Insufficient ultraviolet radiation may therefore influence the development of multiple sclerosis.

Item Type:	Refereed Article
Research Division:	Medical and Health Sciences
Research Group:	Public Health and Health Services
Research Field:	Epidemiology
Objective Division:	Health
Objective Group:	Public Health (excl. Specific Population Health)
Objective Field:	Disease Distribution and Transmission (incl. Surveillance and Response)
Author:	Van der Mei, IAF (Associate Professor Ingrid van der Mei)
Author:	Ponsonby, AL (Professor Anne Ponsonby)
Author:	Dwyer, T (Professor Terry Dwyer)
Author:	Blizzard, CL (Professor Leigh Blizzard)
Author:	Taylor, BVM (Professor Bruce Taylor)
ID Code:	34681
Year Published:	2003
Web of Science® Times Cited:	331
Deposited By:	Menzies Centre
Deposited On:	2005-08-01
Last Modified:	2010-05-05
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