'Fat but powerful' paradox: association of muscle power and adiposity markers with all-cause mortality in older adults from the EXERNET multicentre study.
Level 3 - non-randomized controlled study
Prospective multicentre cohort study with 8.9-year follow-up
PubMed 33727213 · doi:10.1136/bjsports-2020-103720
What was done
The EXERNET multicentre prospective cohort study assessed 2,563 older adults aged 65 to 91 years. Baseline adiposity was measured by body mass index (BMI), waist circumference, body fat percentage (BF%), and fat index. Muscle power was evaluated using the sit-to-stand muscle power test (allometric and relative power). Participants were classified into four groups: lean and powerful (L+P), fat but powerful (F+P), lean but weak, and fat and weak (F+W). Cox proportional hazards regression models adjusted for age, sex, hypertension, smoking status, and walking and sitting times per day were used to evaluate all-cause mortality over a median follow-up of 8.9 years.
What was found
Compared to reference groups, all-cause mortality was significantly reduced in the F+P group when adiposity was classified by BMI (HR = 0.55, p = 0.044) and waist circumference (HR = 0.63, p = 0.049), with a trend toward reduction for BF% (HR = 0.57, p = 0.060), and no significant reduction when classified by fat index. The L+P group demonstrated lower mortality risk across all four measures: BMI (HR = 0.57, p = 0.043), waist circumference (HR = 0.58, p = 0.025), BF% (HR = 0.53, p = 0.021), and fat index (HR = 0.50, p = 0.049). Higher relative power was independently linked to lower mortality (HR = 0.63, p = 0.006 and HR = 0.53, p = 0.011).
Why it matters
These findings suggest that maintaining muscle power provides substantial survival benefits in older adults, counteracting mortality risks associated with adiposity when defined by BMI or waist circumference.
Limits
The observational cohort design precludes causal inference. Confidence intervals for hazard ratios and the precise reference comparator for each model are not reported in the abstract. The survival benefit of high power was blunted when adiposity was measured by fat index rather than BMI or waist circumference. Unmeasured clinical confounders and changes in physical function over the 8.9-year follow-up were not detailed in the abstract.
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