Warfarin Use and Risk for Osteoporosis in Elderly Women. Study of Osteoporotic Fractures Research Group

Background: Vitamin K deficiency may be associated with osteoporosis.

Objective: To assess the effects of warfarin on bone.

Design: Prospective observational study.

Setting: Four centers in the United States.

Participants: 6201 elderly, postmenopausal women.

Measurements: 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.

Results: 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).

Conclusion: In this population, warfarin use did not decrease bone mineral density or increase fracture rates.