Relationship between physical functional status indicators and bone mineral density in older women

Background: Osteoporosis significantly predisposes patients to fragility fractures and a reduced quality of life. Therefore, osteoporosis prevention plays an important role in extending healthy life expectancy. The purpose of this study was to identify whether physical functional status was associated with low bone mineral density, and to determine cut-off values of physical status indicators for osteoporosis. Methods: This cross-sectional study evaluated 343 women aged 60 years or older who were able to walk independently. The measured variables were the body mass index, lumbar and total hip bone mineral density, grip strength, 5-m normal walking speed, one-leg standing time, timed up-and-go test, and skeletal muscle mass using bioelectrical impedance analysis. The associations between physical status indicators and low bone mineral density were analyzed and the cut-off values for detecting osteoporosis were calculated using receiver operating characteristic curve analyses. Results: The prevalence of osteoporosis was 29.2 %. All measured variables significantly differed between the osteoporotic and non-osteoporotic groups (p < 0.05). Multivariate logistic regression analysis showed that the factors associated with osteoporosis were the skeletal muscle mass index, walking speed, and body mass index. In the receiver operating characteristic curve analysis, the cut-off values of the skeletal muscle mass index, walking speed, and body mass index associated with osteoporosis were 6.31 kg/m(2), 1.29 m/s, and 22.6 kg/m(2), respectively. Conclusions: Older women with low bone mineral density have lower skeletal muscle mass, slower walking speed, and lower body mass index. Measuring the skeletal muscle mass index, walking speed, and body mass index might be useful for daily exercise guidance or osteoporosis screening.