Longer sedentary time is associated with increased risk of low pelvic bone density.

BACKGROUND: Prolonged inactivity has been found to be a major contributor to poor bone health. However, limited research has examined the specific relationship between pelvic bone mineral density (BMD) and sedentary time. The study aims to clarify the association between sedentary time and pelvic BMD in adult Americans. METHODS: Data from the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2018 were examined in this cross-sectional investigation. Participants who had comprehensive information on their pelvic BMD and amount of sedentary time were included. We used multivariable linear regression to assess the association between sedentary time and pelvic BMD, and logistic regression to estimate the odds of low BMD across sedentary levels. Potential effect modification and contributing factors were explored using interaction tests and prespecified subgroup analyses. All analyses accounted for the complex NHANES sampling design with survey weights, strata, and primary sampling units. RESULTS: The analysis includes 15,328 individuals. Longer sedentary time was associated with lower pelvic BMD. In the fully adjusted model, the ≥ 8 h/day group had lower pelvic BMD compared with the < 4 h/day reference group (β = -0.018, 95% CI: -0.031, -0.006; P < 0.01). Subgroup and interaction analyses suggested effect modification by body mass index and glucocorticoid use (P for interaction = 0.047 and 0.003, respectively). CONCLUSION: Longer sedentary time is associated with lower pelvic BMD. This finding underscores the importance of controlling sedentary behavior to stop the decline of bone health. Nevertheless, large prospective studies are required to confirm the results.