Fat-Free Mass, Strength, and Sarcopenia are Related to Bone Mineral Density in Older Women

Abstract 

This study examined the association between fat-free mass (FFM) and muscle strength with bone mineral density (BMD), and compared the BMD values between sarcopenic and nonsarcopenic older women. After the exclusion criteria were applied, a total of 246 volunteers (age: 66.51±6.37yr) participated in the analysis. Subjects underwent FFM and BMD evaluation by dual-energy X-ray absorptiometry and quadriceps strength by an isokinetic dynamometer. To address the potential for confounding by height, FFM values were considered relative to body height squared. For fat mass correction, fat-adjusted FFM was calculated. Individuals were classified as sarcopenic if their appendicular FFM was less than 5.45kg/m². All the evaluated FFM indexes were significantly correlated with the measured BMD sites. Sarcopenic individuals presented significantly lower whole body and trochanter BMD, and were significantly more prone to have low BMD. Muscle strength was also correlated with BMD sites; however, when it was expressed relative to body weight, the significance disappeared. Nevertheless, volunteers with low relative strength had higher risk of having low trochanter BMD. It can be concluded, in older women, that FFM is significantly correlated with BMD independently of height and fat mass. Muscle strength was also correlated with BMD, although the correlation was weaker when corrected for body weight. Finally, sarcopenic elderly women were more likely to have low BMD and muscle strength.

Key Words: Bone mineral density, Osteoporosis, Sarcopenia, Strength