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Neurology. 2018 Apr 3;90(14):e1191-e1199. doi: 10.1212/WNL.0000000000005257. Epub 2018 Mar 7.

Sun exposure over the life course and associations with multiple sclerosis.

Author information

1
From the Centre for Brain Health and Faculty of Medicine (Neurology) (H.T., F.Z.), University of British Columbia; Vancouver Coastal Health Research Institute (H.T., F.Z.), British Columbia, Canada; Departments of Nutrition (A.A., K.L.M.) and Epidemiology (A.A.), Harvard T.H. Chan School of Public Health; and Channing Division of Network Medicine (A.A.), Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA. helen.tremlett@ubc.ca.
2
From the Centre for Brain Health and Faculty of Medicine (Neurology) (H.T., F.Z.), University of British Columbia; Vancouver Coastal Health Research Institute (H.T., F.Z.), British Columbia, Canada; Departments of Nutrition (A.A., K.L.M.) and Epidemiology (A.A.), Harvard T.H. Chan School of Public Health; and Channing Division of Network Medicine (A.A.), Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA.

Abstract

OBJECTIVE:

To examine sun exposure and multiple sclerosis (MS) over the life course (ages 5-15 and 16-20 years, every 10 years thereafter).

METHODS:

Cases with MS (n = 151) and age-matched controls (n = 235) from the Nurses' Health Study cohorts completed summer, winter, and lifetime sun exposure history questionnaires. Cumulative ambient ultraviolet (UV)-B (based on latitude, altitude, cloud cover) exposure before MS onset was expressed as tertiles. Seasonal sun exposure was defined as low vs high hours per week (summer [≤9 vs >10 h/wk]; winter [≤3 vs >4 h/wk]). Relative risks (RRs) and 95% confidence intervals (CIs) were estimated via conditional logistic regression with adjustment for body mass index, ancestry, smoking, and vitamin D supplementation.

RESULTS:

Most participants were white (98%); the mean age at MS onset was 39.5 years. Living in high (vs low) UV-B areas before MS onset was associated with a 45% lower MS risk (adjusted RR 0.55, 95% CI 0.42-0.73). Similar reduced risks (51%-52%) for medium or high exposure were observed at ages 5 to 15 years and at 5 to 15 years before MS onset (adjusted p < 0.05). At age 5 to 15 years, living in a high (vs low) UV-B area and having high (vs low) summer sun exposure were associated with a lower MS risk (RR 0.45, 95% CI 0.21-0.96).

CONCLUSION:

Living in high ambient UV-B areas during childhood and the years leading up to MS onset was associated with a lower MS risk. High summer sun exposure in high ambient UV-B areas was also associated with a reduced risk.

PMID:
29514944
PMCID:
PMC5890609
DOI:
10.1212/WNL.0000000000005257
[Indexed for MEDLINE]
Free PMC Article

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