Timing of anti-osteoporosis medications initiation after a hip fracture affects the risk of subsequent fracture: A nationwide cohort study.

Abstract Objective The optimal time after hip fracture to start prophylactic anti-osteoporosis medications (AOMs) remains uncertain, especially in real-world practice. Therefore, we investigated how AOMs initiation timing affects the risk of subsequent osteoporotic fractures, and what factors influence AOMs prescription timing. Method Patients ≥50 years old with diagnostic codes indicating hospitalization for hip fracture (n = 77,930) were sampled from the Taiwan National Health Insurance Research Database; 9986 who were prescribed AOMs ≤1 year after a newly-diagnosed hip fracture were grouped into those who started AOMs from: ≤14 days (early); 15–84 days (very early); 85–252 days (late); and 253–365 days (very late). Associations with fracture-related hospitalizations after an index fracture were analyzed using a multivariate, time-dependent Cox proportional hazards model, and between-group differences compared by log-rank testing. Factors influencing AOMs initiation timing were elucidated using multivariate logistic regression analyses. Results Compared to AOMs initiation from 15 to 84 days, initiation after 252 days was associated with significantly increased risk of fracture-related re-hospitalization (HR = 1.93, 95% CI 1.29–2.89). Both sensitivity and pre-specified subgroup analyses yield similar results. Among patients with high AOMs adherence, the increased risk of subsequent fracture-related hospitalization among very late users was profound (HR = 2.56, 95% CI 1.41–4.64). Conclusion AOMs initiation timing was significantly associated with age, index year, index hospital length of stay, accreditation level and geographic region. After adjusting factors associated with AOMs initiation timing and patients' adherence, the anti-fracture benefit of AOMs still depends crucially on the timely initiation of AOMs.