Longitudinal trajectories of walking speed and risk of incident hip fracture in osteoporosis: a group-based trajectory modeling analysis from HRS, ELSA and SHARE.

Background: Walking speed is an objective indicator of physical function and may predict adverse outcomes. However, its longitudinal patterns and association with hip fracture risk in osteoporosis remain unclear. Methods: Data from HRS, ELSA, and SHARE were analyzed. Participants aged ≥50 years with osteoporosis and no baseline hip fracture were included. Walking speed trajectories were identified using Group-Based Trajectory Modeling. Cox models assessed associations with incident hip fracture, with validation via competing risk and discrete-time models. Dose-response and mediation analyses were also conducted. Results: A total of 14,139 participants were included. During follow-up, 590 hip fractures occurred. Higher baseline walking speed was associated with increased fracture risk in HRS and ELSA but not SHARE. Four trajectory groups were identified, with risk increasing across groups. The high-increasing trajectory showed the greatest risk (HRS: HR = 2.56; ELSA: HR = 4.54). Results were robust across analyses. A linear relationship was observed, and depression and grip strength partially mediated the association. Conclusions: Both baseline and longitudinal increases in walking speed were associated with higher hip fracture risk in osteoporosis, highlighting the importance of dynamic functional assessment.