Predictors of bone mass in healthy older men in the community

Objectives: To determine the predictors of bone mass (in lumbar spine and femoral neck) in healthy older men living in the community. Design: Cross-sectional study. Bone mineral density (BMD) was measured and known predictors of bone mass and bone turnover were assessed. Subjects and setting: 113 independent, healthy men (70 years and over), not taking glucocorticoid therapy and without medical conditions known to affect bone mass and bone turnover, were recruited from recreational and sports clubs in southern Sydney in April/May 1997. Main outcome measures: BMD (measured by dual-energy x-ray absorptiometry); known predictors of bone mass (height; weight; body mass index; calcium level; serum 25-hydroxyvitamin D and free testosterone levels); and markers of bone turnover (serum bone Gla protein and procollagen-l concentrations, and urinary deoxypyridinoline excretion rates). Results: The mean age of the men was 76.6 years (range, 70-92 years). Mean (SE) BMD of the lumbar spine was 1.143 (0.019) g/cm(2) and that of the femoral neck was 0.897 (0.013)g/cm(2). BMD values indicating osteoporosis were found in the lumbar spine in 13 men (11.5%) and in the femoral neck in 35 men (31%). The best predictor of lumbar spine BMD was weight (R=0.37; P=0.001), and weight- and age-predicted femoral-neck BMD (R=0.49; P<0.001). The study group was analysed in two groups with BMD higher or lower than median bone mass corrected for age. Men with lower femoral-neck BMD for age had significantly lower weight, lower lean mass and higher bone Gla protein concentrations. In addition, men with lower lumbar spine BMD for age also had significantly lower fat mass. Conclusions: These data indicate that measures of body composition, such as weight and lean mass, are the main predictors of bone mass in healthy, community-dwelling older men.