Single-point assessment of warfarin use and risk of osteoporosis in elderly men

OBJECTIVES: To determine whether warfarin use, assessed at a single point in time, is associated with bone mineral density (BMD), rates of bone loss, and fracture risk in older men. DESIGN: Secondary analysis of data from a prospective cohort study. SETTING: Six U.S. clinical centers. PARTICIPANTS: Five thousand five hundred thirty-three community-dwelling, ambulatory men aged 65 and older with baseline warfarin use data. MEASUREMENTS: Warfarin use was assessed as current use of warfarin at baseline using an electronic medication coding dictionary. BMD was measured at the hip and spine at baseline, and hip BMD was repeated at a follow-up visit 3.4 years later. Self-reported nonspine fractures were centrally adjudicated. RESULTS: At baseline, the average age of the participants was 73.6 +/- 5.9, and 321 (5.8%) were taking warfarin. Warfarin users had similar baseline BMD as nonusers (n=5,212) at the hip and spine (total hip 0.966 +/- 0.008 vs 0.959 +/- 0.002 g/cm(2), P=.37; total spine 1.079 +/- 0.010 vs 1.074 +/- 0.003 g/cm(2), P=.64). Of subjects with BMD at both visits, warfarin users (n=150) also had similar annualized bone loss at the total hip as nonusers (n=2,683) (-0.509 +/- 0.082 vs -0.421 +/- 0.019%/year, P=.29). During a mean follow-up of 5.1 years, the risk of nonspine fracture was similar in warfarin users and nonusers (adjusted hazard ratio=1.06, 95% confidence interval=0.68-1.65). CONCLUSION: In this cohort of elderly men, current warfarin use was not associated with lower BMD, accelerated bone loss, or higher nonspine fracture risk.