Age-related decline in skeletal muscle mass and function among elderly men and women in Shanghai, China-A cross sectional study

Objective: To investigate the relationship of muscle mass and muscle function with age. Methods and Study Design: The study including 415 participants (aged 60-99 years). Upper (UMM) and lower (LMM) limbs muscle mass and whole body fat free mass (FFM) were measured by bioelectrical impedance analysis. The appendicular skeletal muscle mass (ASM) index (ASM/height(2)) was calculated. Muscle function was assessed by measuring hand grip strength (HGS) and gait speed. Results: Using ASM index cutoff values we found that higher prevalence of sarcopenia in women than in men (33.5% vs 23.6%, p=0.025). In the upper limb, HGS (beta=-0.809) declined more rapidly with age than did UMM (beta=-0.592) in men, but not in women (beta=-0.389 and (beta=-0.486 respectively). In the lower limb, gait speed declined more rapidly than LMM in both men (beta=-0.683 vs beta=-0.442) and women (beta=-1.00 vs (beta=-0.461). The variance of UMM explained 28-29% of the variance of HGS, and LMM explained 7-8% of the variance of gait speed in women and men respectively. In addition to the common predictors (BMI and age), the specific predictors were smoking, exercise and education for FFM and ASM, and smoking, drinking and exercise for HGS (p<0.05). Conclusions: Loss of muscle function is greater than the decline of muscle mass particularly in the upper limbs in men. However, women are more prone to have low muscle mass than the men. Exercise programs need to be designed gender specifically.