Cardiorespiratory fitness is a strong and consistent predictor of morbidity and mortality among adults: an overview of meta-analyses representing over 20.9 million observations from 199 unique cohort studies.
Level 3 - non-randomized controlled study
Overview of systematic reviews and meta-analyses of observational cohort studies
PubMed 38599681 · doi:10.1136/bjsports-2023-107849
What was done
This overview of systematic reviews synthesized evidence from five bibliographic databases (searched from January 2002 to March 2024) evaluating associations between baseline cardiorespiratory fitness (CRF) and health outcomes in adults. The authors identified and included 26 systematic reviews representing 199 unique observational cohort studies with over 20.9 million observations across general and clinical populations.
What was found
High versus low CRF was associated with a substantial reduction in all-cause mortality (HR = 0.47; 95% CI 0.39 to 0.56; 8 meta-analyses). Each 1-metabolic equivalent of task (MET) higher CRF was associated with an 11% to 17% reduction in all-cause mortality (HR = 0.89; 95% CI 0.86 to 0.92, and HR = 0.83; 95% CI 0.78 to 0.88). For incident disease, high versus low CRF showed the largest risk reduction in incident heart failure (HR = 0.31; 95% CI 0.19 to 0.49; 1-MET higher HR = 0.82; 95% CI 0.79 to 0.84; 9 meta-analyses across 12 outcomes). In patients with cardiovascular disease, high versus low CRF conferred a large reduction in cardiovascular mortality (HR = 0.27; 95% CI 0.16 to 0.48). Overall GRADE certainty ranged from very low to moderate.
Why it matters
This umbrella review demonstrates that cardiorespiratory fitness is a robust, dose-dependent predictor of longevity, heart failure risk, and cardiovascular survival across diverse adult populations.
Limits
The underlying evidence comes entirely from observational cohort studies rather than randomized trials, precluding definitive causal inference and leaving open the possibility of residual confounding. The certainty of evidence across outcomes ranged from very low to moderate per GRADE. The abstract does not detail specific CRF measurement methodologies (e.g., direct cardiopulmonary exercise testing vs. estimated fitness) or the degree of primary study overlap between included meta-analyses.
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