Abstract
OBJECTIVE: Associations between sedentary behavior (SB) during leisure time and the risk of osteopenia and osteoporosis are inconclusive. We aimed to examine the impact of replacing sedentary time with equivalent durations of various physical activities on the risk of developing osteoporosis. METHODS: This is a sub-study from the UK Biobank, in which heel bone mineral density (BMD) was measured via ultrasound densitometry among 193,600 participants. A Logistic regression model and an isotemporal substitution model were used in the analyses. RESULTS: In this study, 52,430 osteopenia cases were recorded, of which 2443 were defined as osteoporosis. In comparison to participants with leisure-time SB < 5 h/day, the odds ratio (OR) of osteoporosis risk was 1.38 (95 % confidence interval [CI): 1.17-1.62) for >8 h/day. Replacing 30 min/day of leisure sedentary time with an equal time spent in the walk for pleasure was associated with a 3 % decrease of osteopenia risk and an 8 % decrease of osteoporosis risk, and replacing 3 min of leisure-time SB with an equal amount of strenuous sports was significantly associated with a 4 % reduction in the risk of osteoporosis and osteopenia (OR = 0.96, 95 %CI: 0.93-0.98 and OR = 0.96, 95 %CI: 0.96-0.97). Furthermore, strenuous sports as an alternative to SBs was significantly associated with a lower risk of osteopenia and osteoporosis, especially in participants achieving 1.5-2.5 h of summer light hours. CONCLUSION: Leisure-time SB was positively associated with the risk of osteopenia and osteoporosis. Replacing sedentary time with equal time of PA and achieving 1.5-2.5 h of summer sun exposure could be an effective way to reduce osteopenia and osteoporosis burden.