Association between Daily Sunlight Exposure and Fractures in Older Korean Adults with Osteoporosis: A Nationwide Population-Based Cross-Sectional Study

Abstract

Purpose: We aimed to investigate the association between daily sunlight exposure duration and fractures in older Korean adults with osteoporosis.

Materials and methods: We utilized data from the 2008-2011 Korea National Health and Nutrition Examination Survey. Osteoporosis was diagnosed based on a T-score of ≤-2.5 using dual energy X-ray absorptiometry. The duration of daily sunlight exposure and fracture were assessed via intensive health interviews by trained staff using standardized health questionnaires. Fracture was defined as one or more fractures of the femur, wrist, and spine.

Results: A total of 638 patients with osteoporosis aged ≥65 years were included. The odds ratio (OR) of total fractures was 0.55 times lower in the group with ≥5 h of daily sunlight exposure than in the group with <5 h of exposure after adjusting for age, sex, family history of osteoporosis or fracture, body mass index, bone mineral density of the femoral neck, serum 25-hydroxyvitamin D, current smoking, alcohol intake, daily calcium intake, and physical activity [95% confidence interval (CI) 0.31-0.97, p=0.040]. In patients with vitamin D insufficiency, the OR of total fracture was 0.52 times lower in the group with ≥5 h of daily sunlight exposure than in the group with less exposure after adjusting the above variables (95% CI 0.28-0.97, p=0.041).

Conclusion: Sunlight exposure for ≥5 h a day was significantly associated with a decreased OR of fracture in older Korean adults with osteoporosis. This association was also significant in patients with vitamin D insufficiency.