Impact of Relative Muscle Power on Hospitalization and All-Cause Mortality in Older Adults.
Level 3 - non-randomized controlled study
Prospective cohort study tracking clinical outcomes over follow-up
PubMed 34407184 · doi:10.1093/gerona/glab230
What was done
Researchers analyzed 1,928 older adults from the Toledo Study for Healthy Aging to examine whether lower-limb muscle power predicts hospitalization and all-cause mortality. Muscle power was evaluated using the 5-repetition sit-to-stand test, normalized to body mass (relative power), and stratified into sex-specific tertiles and an inability-to-perform group. Mean follow-up was 3.3 years for hospitalizations and 6.3 years for all-cause mortality. Multivariable models adjusted for age, physical activity, body mass index, education, depression, comorbidities, disability, and handgrip strength.
What was found
Compared to the high relative power group, age-adjusted hospitalization risk was elevated in men with low power (HR 2.1, 95% CI 1.2-3.6) and women with low (HR 1.8, 95% CI 1.2-2.7) or very low power (HR 4.7, 95% CI 3.0-7.4). After full multivariable adjustment, hospitalization risk remained statistically elevated in women with very low relative power (HR 2.8, 95% CI 1.6-4.9) but not in men (HR 1.6, 95% CI 0.9-2.9). For all-cause mortality, age-adjusted risk was higher in the very low power group for both men (HR 2.3, 95% CI 1.4-3.9) and women (HR 2.9, 95% CI 1.6-5.3). Following full adjustment, mortality risk remained significantly higher only in men with very low relative power (HR 2.1, 95% CI 1.1-3.8; women HR 1.6, 95% CI 0.8-3.2).
Why it matters
Assessing lower-body muscle power via a simple sit-to-stand protocol provides independent prognostic information for adverse outcomes in older adults, even after accounting for standard functional measures like handgrip strength.
Limits
The observational design cannot establish causality. Power was indirectly derived from sit-to-stand performance rather than direct dynamometry. Findings come from a single regional cohort in Spain, and fully adjusted mortality associations lost statistical significance in women.
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