Warfarin use and risk for osteoporosis in elderly women. Study of Osteoporotic Fractures Research Group.

<bold>Background: </bold>Vitamin K deficiency may be associated with osteoporosis.<bold>Objective: </bold>To assess the effects of warfarin on bone.<bold>Design: </bold>Prospective observational study.<bold>Setting: </bold>Four centers in the United States.<bold>Participants: </bold>6201 elderly, postmenopausal women.<bold>Measurements: </bold>Self-reported warfarin use, bone mineral density at the hip and the heel, hip bone loss over 2 years, and fractures during 3.5 years of follow-up. Analyses were adjusted for baseline differences, age, weight, and estrogen use.<bold>Results: </bold>Compared with warfarin nonusers (n = 6052), warfarin users (n = 149) more frequently had poor health, involuntary weight loss, nonthiazide diuretic use, and frailty but had similar bone mineral density at the hip (difference, 1.6% [95% CI, -0.7% to 4.1%]) and heel (difference, 2.1% [CI, -1.6% to 5.6%]). Users and nonusers had similar rates of bone loss (1.1% and 0.8%; P = 0.18) and fractures (relative hazard, 1.0 [CI, 0.60 to 1.71).<bold>Conclusion: </bold>In this population, warfarin use did not decrease bone mineral density or increase fracture rates. [ABSTRACT FROM AUTHOR]