Relationship of body composition with prevalence of osteoporosis in central south Chinese postmenopausal women

OBJECTIVES: To elucidate the relationship between body composition and bone mineral density (BMD) and the prevalence of osteoporosis in central south Chinese postmenopausal women. METHODS: A cross-sectional study was conducted on 954 healthy central southern Chinese postmenopausal women, aged 50-82. Total body, lumbar spine and left femur BMD and total body soft tissue composition were measured by dual X-ray absorptiometry. RESULTS: Among the study population, 578 (60.5%) subjects were without osteoporosis and 376 (39.4%) subjects were osteoporotic. The osteoporotic women were older, shorter and thinner, had an earlier age at menopause, a lower BMD and bone mineral content (BMC) of the total body and at different sites, and had lower body mass and body mass components than the women without osteoporosis. Both fat mass and lean mass were positively correlated with age at menopause, height, weight, body mass index (BMI) and BMD at all sites. Fat mass and lean mass were also inversely correlated with age and years since menopause (P<0.05). After controlling for age, age at menopause and height, both fat mass and lean mass were positively correlated with BMD at the lumbar(1-4) spine, the femoral neck and the total hip. Fat mass was the most significant determinant of BMD at the lumbar(1-4) spine with a higher R(2) change and a partial R(2) compared with that of lean mass, while lean mass had more impact on the total hip values. Either a fat mass below 18.4 kg or a lean mass below 33.9 kg was correlated with a higher prevalence of osteoporosis at the lumbar spine or total hip. CONCLUSIONS: In central south Chinese postmenopausal women, both fat mass and lean mass are correlated with BMD at the lumbar spine and hip. Fat mass was the most significant determinant of BMD at the lumbar spine, while lean mass had more impact on the total hip value. Both lower values of fat mass and lean mass are related to a higher prevalence of osteoporosis at either the lumbar spine or the total hip. Thus, it is important to maintain a reasonable body weight to balance bone health and other metabolic disorders.