Sit-to-stand power vs. handgrip strength for the assessment of muscle function in older people: Impact on functional ability and mortality in the Toledo study for healthy aging

OBJECTIVE: This study aims to compare the association of low absolute and allometric sit-to-stand (STS) power and handgrip strength with adverse outcomes and all-cause mortality in older male and female. METHODS: 2134 adults aged ≥65 years (mean age 74.2 ± 6.8 years; 54.4% female) were assessed for handgrip strength and STS power. Both absolute handgrip strength and STS power were normalized by height squared (i.e., allometric values). The impact of low absolute and allometric STS power and handgrip strength on low functional ability (low usual gait speed (UGS), cognitive impairment, and disability) and all-cause mortality was evaluated through sex-stratified binary logistic regression and Cox proportional hazard models using sex-specific cut-off points. RESULTS: In male, low absolute and low allometric STS power were associated with lower functional ability and mortality (pooled OR [95%CI] = 2.29 [1.60-3.28] and 2.21 [1.53-3.19], respectively), similar to low absolute and allometric handgrip strength (pooled OR [95%CI] = 1.57 [1.08-2.28] and 1.67 [1.16-2.40], respectively). However, low absolute STS power was more strongly associated with low UGS than low absolute handgrip strength (p = 0.003), while a trend was noted for their allometric equivalents (p = 0.072). In female, low absolute and low allometric STS power were associated to lower functional ability and mortality (pooled OR [95%CI] = 1.81 [1.30-2.53] and 1.66 [1.21-2.29], respectively), as well as low absolute and low allometric handgrip strength (pooled OR [95%CI] = 1.66 [1.19-2.31] and 1.70 [1.24-2.33], respectively), with no significant differences between muscle function measures (p > 0.05). CONCLUSION: Low STS power showed a stronger association with low UGS than low handgrip strength in male. However, their overall impact on functional ability and mortality was similar between muscle function measures in older male and female.