Characteristics of Body Composition and Relationship between Muscle Mass and Muscle Strength among Elderly Women in Different Age Groups

Age-related changes in the body composition of older adults differ among age groups. The purpose of the present study was to clarify the characteristics of body compositions in young (age, 65 - 74 years; yE group) and old (age, ≥75 years; oE group) elderly women, and compare the relationship between muscle mass and strength in elderly women with that in young women for preventing motor function loss in older adults. A total of 30 elderly and 45 young women aged ≥ 65 and 19 - 22 years, respectively, participated in this study. The participants underwent body composition measurement via bioelectrical impedance analysis and examinations of handgrip and leg muscle strength. The age-related body composition changes varied among age groups. Compared with young women, fat-free mass (FFM) in the yE group did not decrease significantly; however, fat mass (FM) and waist-hip ratio (WHR) were significantly greater. Compared with the yE group, decreases in FFM, FM, and WHR in the oE group were significant; furthermore, the decrease in FM measurements was attributed to the loss of FM in the trunk and limbs (upper and lower). The measurement results suggested that the greater FM decrease in the oE group was characterized by decreases in both visceral and subcutaneous fat. In the yE group, the muscle mass was comparable to that in young women; however, there was a remarkable reduction in the lower-limb muscle mass (9% - 10%). In the oE group, muscle mass was reduced in all body parts, including upper and lower limbs and trunk. In young women, significant positive correlations between muscle mass and muscle strength in the upper and lower limbs were observed. No such correlations in the lower limbs were found in elderly women, indicating that muscle mass is not proportionally reflected in muscle strength. In conclusion, for improving and maintaining the health of elderly women, especially those above the age of 75 years, it is important to maintain muscle mass, including muscle strength, and prevent the loss of muscle quality.