Bone-muscle indices as risk factors for fractures in men: the Osteoporotic Fractures in Men (MrOS) Study.

ABSTRACT

OBJECTIVE: To assess bone-muscle (B-M) indices as risk factors for incident fractures in men. METHODS: Participants of the Osteoporotic Fractures in Men (MrOS) Study completed a peripheral quantitative computed tomography scan at 66% of their tibial length. Bone macrostructure, estimates of bone strength, and muscle area were computed. Areal bone mineral density (aBMD) and body composition were assessed with dual-energy X-ray absorptiometry. Four year incident non-spine and clinical vertebral fractures were ascertained. B-M indices were expressed as bone-to-muscle ratios for strength, mass and area. Discriminative power and hazards ratios (HR) for fractures were reported. RESULTS: In 1163 men (age 77.2±5.2 years, body mass index (BMI) 28.0±4.0 kg/m(2), 4.1±0.9 follow-up years, 7.7% of men ⋝1 fracture), B-M indices were smaller in fractured men except for bending and areal indices. Smaller B-M indices were associated with increased fracture risk (HR 1.30 to 1.74) independent of age and BMI. Strength and mass indices remained significant after accounting for lumbar spine but not total hip aBMD. However, aBMD correlated significantly with B-M indices. CONCLUSION: Mass and bending B-M indices are risk factors for fractures in men, but may not improve fracture risk prediction beyond that provided by total hip aBMD.