Total And Regional Skeletal Muscle Mass In Middle-aged And Elderly Japanese Men And Women

Abstract

PURPOSE To examine the influence of age and gender on total and regional (arm, trunk and leg) skeletal muscle (SM) mass in middle-aged and elderly Japanese men and women. METHODS 395 middle-aged (183 men and 212 women, aged42.4±4.2yr [35–49yr]) and 168 elderly subjects (79 men and 89 women, mean age 73.5±3.5yr [70–91yr]) were volunteered for the study. All subjects were free of orthopaedic abnormalities and diagnosed neurological or cardiovascular disease. Muscle thickness was measured by B-mode ultrasound (5 MHz scanning head) at 6 sites on anatomical SM belly (anterior and posterior upper arm, abdomen, subscapular, anterior and posterior thigh). Total and regional (arm, trunk and leg) SM mass were estimated using prediction equations (MSSE 36(5): S74, 2004), which was developed based on the relationship between ultrasound-measured muscle thickness and MRI-measured SM mass. RESULTS Total SM mass in elderly men and women was 17.1±2.6and 11.4±1.8 kg, which was lower (P < 0.01) than in middle-aged men (21.5±2.3kg) and women (14.1±1.6kg), respectively. The ratio of total SM mass to body mass in elderly subjects (men 32.0±3.3%, women 24.3±2.3%) was lower (P < 0.01) than in middle-aged subjects (men 34.1 ±2.5%, women 26.0±2.4%). The difference of total SMmass between middle-aged and elderly subjects was 4.4kg in men and 2.7kg in women. Arm, trunk and leg SMmass in elderly subject (men 1.8±0.4, 7.4±1.1 and 8.0±1.6kg; women 1.2±0.2, 5. 1±0.7 and 5.0±1.2kg, respectively) was lower (P < 0.01) compared with middle-aged subjects (men 2.5±0.3, 8.5±1.1 and 10.5±1.4kg; women 1.5±0.2, 5.6±0.6 and 7.0±1.1kg, respectively). The difference of arm, trunk and leg SMmass between middle-aged and elderly subjects was 0.7 (17%), 1.1 (25%) and 2.5kg (58%) in men and 0.3 (10%), 0.5 (17%) and 2.0kg (73%) in women. CONCLUSIONS These results indicated that 1) elderly subjects possessed about 25% less total SM than middle-aged subjects in both men and women, and 2) about 60–70% of this difference in whole body SM loss may be attributable to loss of leg SM mass.