Fracture Rates in Patients Discontinuing Alendronate Treatment in Real Life: a Population-based Cohort Study

Introduction: Information on fracture risk in patients discontinuing ALN in a real-life setting is sparse. We aimed to examine ALN discontinuation patterns, compare fracture rates in patients discontinuing versus continuing ALN after 5 years of treatment, and define determinants of fractures in ALN discontinuers.

Methods: A nationwide population-based cohort study using Danish health registry data. Our source population was individuals who had redeemed ≥ 2 ALN prescriptions between January 1, 1995, and September 1, 2017.

Results: We found that 25% of all ALN initiators used ALN for less than 1 year and 43% continued treatment for at least 5 years. We classified n = 1865 as ALN discontinuers and n = 29,619 as ALN continuers. Using Cox proportional hazards regression analysis and an "as-treated" approach, we observed no increased risk of any fracture (incidence rate ratio (IRR) 1.06, 95% CI 0.92-1.23), vertebral fracture (IRR 0.59, 95% CI 0.33-1.05), hip fracture (IRR 1.04, 95% CI 0.75-1.45), or major osteoporotic fracture (IRR 1.05, 95% CI 0.88-1.25) in the ALN discontinuers compared to continuers during a follow-up time of 1.84 ± 1.56 years (mean ± SD) and 2.51 ± 1.60 years, respectively. ALN re-initiation was a major determinant of follow-up among the discontinuers. Old age (> 80 vs. 50-60 years, unadjusted IRR 2.92, 95% CI 1.18-7.24) was the strongest determinant for fractures following ALN discontinuation.

Conclusion: In a real-world setting, less than 50% continued ALN treatment for 5 years. We found no difference in the risk of fractures in patients discontinuing versus continuing ALN after 5 years.