Age-related site-specific muscle wasting of upper and lower extremities and trunk in Japanese men and women.

The purpose of this study was to examine the age-related site-specific muscle loss of the upper and lower extremities and trunk in men and women. Japanese nonobese adults aged 20-79 (n = 1559, 52 % women) had muscle thickness (MTH) measured by ultrasound at nine sites on the anterior and posterior aspects of the body. An MTH ratio located in the anterior and posterior aspects of the upper arm, upper leg, lower leg, and trunk was calculated. Site-specific muscle loss was defined as a ratio of MTH > 2 standard deviations below the mean for young adults in each segment. Age was inversely correlated (p < 0.001) to upper-leg MTH ratio in men (r = -0.463) and women (r = -0.541). Age was correlated positively to upper-arm MTH ratio and inversely to trunk MTH ratio in men (r = 0.191 and r = -0.238, both p < 0.001) and women (r = 0.102, p = 0.004 and r = -0.446, p < 0.001). Weak correlations were observed between age and lower-leg MTH ratios in men (r = 0.015, p = 0.682) and women (r = 0.086, p = 0.015). The prevalence of site-specific upper-leg muscle loss showed an age-related increasing pattern in men (6 % for ages 30-39, 21 % for ages 50-59, and 38 % for ages 70-79) and women (15 % for ages 30-39, 32 % for ages 50-59, and 50 % for ages 70-79). For other segments, however, the prevalence rate of site-specific muscle loss was relatively low throughout the age groups in men and women, although higher rates were observed in the older group. These results suggest that the anterior/posterior MTH ratio of the upper leg may be useful in providing an earlier diagnosis for site-specific muscle loss.