Incident long-term warfarin use and risk of osteoporotic fractures: propensity-score matched cohort of elders with new onset atrial fibrillation.

Abstract

Association between warfarin use and fracture risk is unclear. We examined the association between long-term warfarin use and fracture risk at the hip, spine, and wrist in elders. No significant association was found between long-term warfarin use and fracture risk, despite biological plausibility. Prior studies examining the association of warfarin use and osteoporotic fractures have been conflicting, potentially related to methodological limitations. Thus, we examined the association of long-term warfarin use with risk of hip, spine, and wrist fractures among older adults with atrial fibrillation, attempting to address prior methodologic challenges. We included men and women ≥ 65 years of age with incident atrial fibrillation and without prior history of fractures from The Health Improvement Network followed between 2000 and 2010. Long-term warfarin use was defined in two ways: (1) warfarin use ≥ 1 year; (2) warfarin use ≥ 3 years. Propensity-score matched cohorts of warfarin users and nonusers were created to evaluate the association between long-term warfarin use and risk of hip, spine, and wrist fractures separately as well as combined, using Cox-proportional hazards regression models. Among >20,000 participants with incident atrial fibrillation, the hazard ratios (HR) for hip fracture with warfarin use ≥ 1 and ≥ 3 years, respectively, were 1.08 (95%CI 0.87, 1.35) and 1.13 (95% CI 0.84, 1.50). Similarly, no significant associations were observed between long-term warfarin use and risk of spine or wrist fracture. When risk of any fracture was assessed with warfarin use, no association was found [HR for warfarin use ≥ 1 year 0.92 (95%CI 0.77, 1.10); HR for warfarin use ≥ 3 years 1.12 (95%CI 0.88, 1.43)]. Long-term warfarin use among elders with atrial fibrillation was not associated with increased risk of osteoporotic fractures and therefore does not appear to necessitate additional surveillance or prophylaxis.