Duration of Bisphosphonate Drug Holidays and Associated Fracture Risk
Jeffrey R. Curtis, Kenneth G. Saag, Tarun Arora, Nicole C. Wright, Huifeng Yun, Shanette G. Daigle, Robert Matthews, Elizabeth Delzell
Abstract
BACKGROUND: Discontinuation of bisphosphonates (BP) or a "drug holiday" after several years of treatment is increasingly common. However, the association of drug holiday duration with future fracture risk is unclear. OBJECTIVES: We evaluated the rate of fracture in relation to various lengths of drug holidays among women receiving long-term BP therapy. RESEARCH DESIGN: Observational cohort study using US Medicare data 2006-2016. Incidence rates (IRs) and Cox proportional hazards models were used to evaluate the rate and adjusted hazard ratios (aHRs) controlling for potential confounders. SUBJECTS: Women aged 65 years and above enrolled in fee-for-service Medicare who had been adherent (≥80%) to alendronate, risedronate, or zoledronate for ≥3 years. MEASURES: Hip, humerus, distal forearm, and clinical vertebral fracture. RESULTS: Among 81,427 eligible women observed for a median (interquartile range) of 4.0 (2.5, 5.3) years, 28% of women underwent a drug holiday. In the alendronate cohort (73% overall), the IR of hip fracture among women who discontinued BP for >2 years was 13.2 per 1000 person-years. Risk was increased (aHR=1.3, 1.1-1.4) versus continuing therapy (IR=8.8, referent). Rates were elevated for humerus fracture with discontinuation >2 years (aHR=1.3, 1.1-1.66) and for clinical vertebral fracture with discontinuation >2 years (aHR=1.2, 1.1-1.4). Results were similar for risedronate, zoledronate, and ibandronate for hip and clinical vertebral fracture. CONCLUSION: Discontinuing alendronate beyond 2 years was associated with increased risk of hip, humerus, and clinical vertebral fractures.