Living in high ambient UV-B areas during childhood and the years leading up to multiple sclerosis (MS) onset was associated with a lower MS risk, according to a recent study. Furthermore, high summer sun exposure in high ambient UV-B areas was also associated with a reduced risk. Persons with MS (n=151) and age-matched controls (n=235) from the Nurses' Health Study cohorts completed questionnaires that assessed summer, winter, and lifetime sun exposure history. Relative risks and 95% confidence intervals were estimated via conditional logistic regression with adjustment for body mass index, ancestry, smoking, and vitamin D supplementation. They found:
- 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.
- 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.
- 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.
Tremlett H, Zhu F, Ascherio A, Munger KL. Sun exposure over the life course and associations with multiple sclerosis. [Published online ahead of print March 7, 2018]. Neurology. doi:10.1212/WNL.0000000000005257.