Association of accelerometer-derived sleep characteristics with incident osteoporosis: a prospective cohort study from the UK Biobank.

Background: Osteoporosis (OP) is a common metabolic bone disease whose onset and progression are influenced by sleep patterns. However, previous related studies have mostly relied on self-reported sleep data and have often been confined to a single dimension such as sleep duration. Therefore, this study aimed to evaluate the associations between multidimensional, objective sleep characteristics and OP. Methods: This study was based on the UK Biobank and included 72,211 participants. Five objective sleep metrics were derived from 7 consecutive days of wrist accelerometer data: sleep duration, sleep efficiency, sleep regularity index, sleep midpoint, and relative amplitude. Incident OP events were identified through linkage with electronic medical records. Multivariable Cox proportional hazards models were used to examine the associations between objective sleep metrics and OP. Restricted cubic splines (RCS) were applied to test potential nonlinear relationships. Interaction analyses and sex-stratified subgroup analyses were also conducted based on the above results. Results: Average sleep duration (HR = 0.91, 95% CI: 0.87-0.95; Conclusions: Longer objective sleep duration, higher sleep efficiency, and stronger relative amplitude were independently associated with a lower risk of OP. The association between sleep duration and OP also varied by relative amplitude. These findings suggest that objective sleep characteristics and behavioral rest-activity rhythmicity may be relevant to OP risk, although further mechanistic and interventional studies are needed to clarify causality.