The exponential increase in the incidence of fragility fractures in older people is attributed to attenuation of both bone strength and neuromuscular function. Decrease in bone mineral density (BMD) does not entirely explain this increase. The objective of this study is to investigate the effect of age on various parameters related to bone health with aging, and to identify combinations of factors that collectively express the bone metabolic state in healthy postmenopausal women. Height, weight, and grip strength were measured in 135 healthy postmenopausal volunteer women. Hip BMD, biomechanical indices derived from quantitative computed tomography (QCT), cross-sectional areas of muscle and fat of the proximal thigh, and various biochemical markers of bone metabolism were measured. A smaller group of factors explanatory for bone health was identified using factor analysis and each was newly named. As a result, the factors bone mass, bone turnover, bone structure, and muscle strength had the greatest explanatory power for assessing the bone health of healthy postmenopausal women. Whereas dual X-ray absorptiometry parameters only loaded on the factor bone mass, QCT parameters loaded on both the factors bone mass and bone structure. Most bone turnover markers loaded on the factor bone turnover, but deoxypyridinoline loaded on both bone turnover and muscle strength. Age was negatively correlated with bone mass (r = −0.49, p < 0.001) and muscle strength (r = −0.67, p < 0.001). We conclude that aging is associated as much with muscle weakening as with low BMD. More attention should be paid to the effects of muscle weakening during aging in assessments of bone health.
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