Abstract
The study aimed to investigate which combined muscle mass and strength among four different combinations might be a risk factor for mobility limitation and falls in older adults. A total of 284 older adults participated in this study from baseline until the 4-year follow-up. We assessed the appendicular skeletal muscle mass index (AMI) using bioelectric impedance analysis. Additionally, the appendicular strength Z-score (ASZ) based on the hand-grip strength for the upper extremity and peak reaction force during sit-to-stand movement for the lower extremity were measured at baseline. The participants were classified into 4-group according to their AMI and ASZ score: Low AMI and Low ASZ; Low AMI; Low ASZ; and Normal. Mobility limitation and falls were assessed by a self-reported questionnaire at baseline and during follow-up. We used a Cox regression analysis with an adjustment for sex, age, body mass index, knee pain, and back pain. Among participants with no mobility limitation at baseline, the hazard ratio of any new mobility limitation was 5.54 (95% CI 2.24–13.69) in Low AMI and Low ASZ compared with Normal. As for participants with no falls at baseline, the hazard ratio of any new incident falls was 4.01 (95% CI 1.83–8.82) in Low AMI and Low ASZ, 2.05 (95% CI 1.11–3.77) in Low ASZ compared with Normal. These results suggest that the type of combined low muscle mass and low strength is an important risk factor for mobility limitation and falls. Moreover, low strength alone may independently predict incident falls in older adults.