Abstract
OBJECTIVE: The association between time spent in outdoor light (TOL), genetic predisposition, and the risk of osteoporosis (OP) remains unclear. This study aimed to quantify the association between TOL and OP risk, and to evaluate whether genetic predisposition modifies this relationship.
METHODS: Data from the UK Biobank on 326,216 participants based on self-reported TOL, estimated bone mineral density (eBMD), and hospital inpatient records for OP diagnosis. A polygenic risk score (PRS) for OP was calculated and categorized into tertiles. We used generalized linear models, Cox proportional hazards models, and Laplace regression to evaluate the cross-sectional and longitudinal associations between TOL, PRS, and OP risk.
RESULTS: Higher average TOL was associated with increased eBMD (β = 0.0021 g/cm2, 95% CI: 0.0018-0.0024) and lower OP risk (OR = 0.9739, 95% CI: 0.8839-0.9952) in cross-sectional analysis. Participants who spent more than 3 h/day in outdoor light during summer had a reduced risk of incident OP (HR = 0.9505, 95% CI: 0.9088-0.9942) and experienced a delayed by 0.36 years (50th percentile difference = 0.3634, 95% CI: 0.0794-0.6473), compared with those exposed ≤3 h/day. Subgroup analysis indicated an additive effect of limited TOL and high genetic risk on OP susceptibility.
CONCLUSION: Prolonged exposure to outdoor light is associated with higher eBMD and a lower risk of developing OP, even among individuals with high genetic susceptibility. These findings suggest that increasing TOL may be a modifiable lifestyle factor to reduce OP risk, especially in genetically predisposed populations.