This article requires a subscription to view the full text. If you have a subscription you may use the login form below to view the article. Access to this article can also be purchased.
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.
Glossary
- BMI=
- body mass index;
- CI=
- confidence interval;
- MS=
- multiple sclerosis;
- NHS=
- Nurses' Health Study;
- RR=
- relative risk;
- UV=
- ultraviolet
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received September 11, 2017.
- Accepted in final form January 8, 2018.
- © 2018 American Academy of Neurology
AAN Members
We have changed the login procedure to improve access between AAN.com and the Neurology journals. If you are experiencing issues, please log out of AAN.com and clear history and cookies. (For instructions by browser, please click the instruction pages below). After clearing, choose preferred Journal and select login for AAN Members. You will be redirected to a login page where you can log in with your AAN ID number and password. When you are returned to the Journal, your name should appear at the top right of the page.
AAN Non-Member Subscribers
Purchase access
Disputes & Debates: Rapid online correspondence
NOTE: All authors' disclosures must be entered and current in our database before comments can be posted. Enter and update disclosures at http://submit.neurology.org. Exception: replies to comments concerning an article you originally authored do not require updated disclosures.
- Stay timely. Submit only on articles published within the last 8 weeks.
- Do not be redundant. Read any comments already posted on the article prior to submission.
- 200 words maximum.
- 5 references maximum. Reference 1 must be the article on which you are commenting.
- 5 authors maximum. Exception: replies can include all original authors of the article.
- Submitted comments are subject to editing and editor review prior to posting.