Physical Activity, Sunshine Duration, and Osteoporotic Fractures: A Nested Case-Control Study

This study examined the associations between the occurrence of osteoporotic fractures in detailed sites and combined physical activity (PA) and sunshine duration (SD). Data from the Korean National Health Insurance Service-National Health Screening Cohort for 7-year periods and from the Korea Meteorological Administration were used. Osteoporotic fractures (n = 12,103), including vertebral fractures, hip fractures, and distal radius fractures, and matched controls (n = 24,206) were selected in 1:2 ratios by age, sex, income, and region of residence. PA was classified as moderate- to high-intensity PA (High PA) and low-intensity PA (Low PA). SD was classified as Short SD (<6.1 h) and Long SD (≥6.1 h). Conditional logistic regression was used to calculate the odds ratios (ORs) with 95%-confidence intervals (CIs) of the combined PA and SD groups for the occurrence of each osteoporotic fracture. Compared to 'Low PA + Short SD', the adjusted ORs (95% CIs) for vertebral fracture in 'High PA + Short SD' and 'High PA + Long SD' were 0.83 (0.76-0.91) and 0.84 (0.77-0.92), respectively. Hip/distal radius fractures were not associated with the combined PA and SD group. We suggest that a higher intensity of PA is inversely associated with the risk of vertebral fracture.