University of California, San Francisco, and San Francisco Veterans Affairs Medical Center, USA. sophie_jamal@quickmail.ucsf.edu
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.