Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational cohort studies
PubMed 19454641 · doi:10.1001/jama.2009.681
What was done
A systematic review and random-effects meta-analysis of observational cohort studies from MEDLINE (1966–2008) and EMBASE (1980–2008) evaluated the quantitative relationship between baseline cardiorespiratory fitness (CRF) and subsequent all-cause mortality or combined coronary heart disease/cardiovascular disease (CHD/CVD) events in healthy men and women. CRF was estimated as maximal aerobic capacity (MAC) in metabolic equivalent (MET) units and categorized as low (<7.9 METs), intermediate (7.9–10.8 METs), or high (≥10.9 METs).
What was found
From 33 eligible studies (102,980 participants and 6,910 cases for all-cause mortality; 84,323 participants and 4,485 cases for CHD/CVD events): - Per 1-MET higher level of MAC, pooled risk ratios (RRs) were 0.87 (95% CI, 0.84–0.90) for all-cause mortality and 0.85 (95% CI, 0.82–0.88) for CHD/CVD events. - Comparing low CRF with high CRF, the RR was 1.70 (95% CI, 1.51–1.92; P < .001) for all-cause mortality and 1.56 (95% CI, 1.39–1.75; P < .001) for CHD/CVD events. - Comparing low CRF with intermediate CRF, the RR was 1.40 (95% CI, 1.32–1.48; P < .001) for all-cause mortality and 1.47 (95% CI, 1.35–1.61; P < .001) for CHD/CVD events.
Why it matters
This study provides quantitative evidence that higher cardiorespiratory fitness substantially lowers the risk of all-cause mortality and cardiovascular disease in healthy individuals, with each 1-MET increase associated with a 13% to 15% risk reduction.
Limits
All included studies were observational cohorts, which cannot establish causality and remain subject to residual confounding. The abstract does not report specific follow-up durations, demographic breakdowns (e.g., sex ratio, age ranges), or how differences in exercise testing protocols across primary studies were standardized.
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