Age- And Sex-related Differences In Body Composition, Muscle Mass, Strength, Physical Function, Quality, And Specific Muscle Strength Community-dwelling Older Adults

Age-related muscle performance decline precedes muscle mass loss, increasing the focus on muscle quality research, as assessed via specific muscle strength, impedance, and ultrasound. However, specific age-related differences in these parameters in older adults remain unclear. PURPOSE: To examine the association between age and age-related differences in muscle performance, volume, and various muscle quality parameters in older adults. METHODS: A cross-sectional survey was conducted involving 1,381 individuals (mean age 72 years; 704 females). Muscle mass and volume were evaluated using the appendicular lean mass index (ALMI) via bioelectrical impedance spectroscopy (BIS), and thigh muscle thickness (MT) via ultrasonography. Physical function was assessed using the 5-times-chair-stand and vertical jump index (jumping height body weight: VJI). Muscle strength was assessed using handgrip strength (HG) and knee extension strength (KES). Muscle quality indicators included specific muscle strength parameters (HG/ALM and KES/MT) and muscle composition parameters (whole-body and thigh phase angle (PhA) via BIS, and thigh echo-intensity via ultrasonography). The sex-stratified association between age and these parameters was calculated using regression analysis, with the mean value of each muscle item set at 100%. RESULTS: All variables were significantly associated with age. The lower limb measures showed a steeper slope than the upper limb measures. ALMI (male: -0.9%; female: -0.6%) and MT (male: -1.0%; female: -1.2%) had negative associations, while muscle strength and physical function VJI (male: -3.6%; female: -3.9%), KES (male: -2.4%; female: -2.5%), and chair-stand (male: 1.6%; female: 1.7%) showed a steeper slope. Muscle quality indicators KES/MT (male: -1.5%; female: -1.4%), thigh-PhA (male: -1.7%; female: -1.6%), whole-body-PhA (male: 1.3%; female: 1.1%), and echo-intensity (male: 1.1%; female: 0.5%) showed a steady slope, whereas HG/ALM (male: -0.4%; female: -0.3%) exhibited minimal slope. CONCLUSION: The association between these parameters and age showed different associations, which might help identify the mechanisms of physical decline and develop intervention strategies. Supported by: JSPS KAKENHI 23KJ0273 for YA, 24H00683 for YY, and 19 K20140, 22H03525, and 24 K22286 for TY.