Past exposure to sun, skin phenotype, and risk of multiple sclerosis: case-control study.
OBJECTIVE
To examine whether past high sun exposure is associated with a reduced risk of multiple sclerosis.


METHODS
Population based case-control study.


METHODS
Tasmania, latitudes 41-3 degrees S.


METHODS
136 cases with multiple sclerosis and 272 controls randomly drawn from the community and matched on sex and year of birth.


METHODS
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.


CONCLUSIONS
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.
van der Mei
I A F
IA
Menzies Centre for Population Health Research, University of Tasmania, Hobart, TAS 7000, Australia. Ingrid.vanderMei@utas.edu.au
Ponsonby
A-L
AL
Dwyer
T
T
Blizzard
L
L
Simmons
R
R
Taylor
B V
BV
Butzkueven
H
H
Kilpatrick
T
T
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D016022:Case-Control Studies; D002648:Child; D004307:Dose-Response Relationship, Radiation; D004781:Environmental Exposure; D006801:Humans; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000235:genetics*; D016017:Odds Ratio; D010641:Phenotype; D010787:Photosensitivity Disorders / Q000235:genetics; D012307:Risk Factors; D012621:Seasons; D013472:Sunlight / Q000009:adverse effects*