Key numbers
0.87
Pooled relative risk of cardiovascular death per 1-MET higher fitness (Han 2022)
0.67
Summary relative risk of death from any cause, intermediate versus lowest fitness (Han 2022)
0.47
Hazard ratio for death from any cause, high versus low fitness, general populations (Lang 2024)
0.27
Hazard ratio for cardiovascular death, high versus low fitness, people with cardiovascular disease (Lang 2024)
What the studies measured
In this research, cardiorespiratory fitness was measured or estimated from exercise-test performance, often expressed in metabolic equivalent units (METs); not every cohort measured oxygen uptake directly from expired gas. Kodama and colleagues (2009) pooled 33 observational cohort studies; for death from any cause, that meant 102980 participants and 6910 cases from healthy populations.
Han and colleagues (2022) pooled 34 cohort studies to look at the dose-response link between fitness and death from all causes, from cardiovascular disease and from cancer in a healthy population.
What the meta-analyses found
In Kodama's analysis, better fitness went with a lower risk of death from any cause and of coronary heart disease or cardiovascular events. People with low fitness had a risk ratio for death from any cause of 1.40 compared with intermediate fitness, and 1.70 compared with high fitness. Each 1-MET higher level of maximal aerobic capacity went with a pooled risk ratio of 0.85 for heart and cardiovascular events (95 percent confidence interval 0.82 to 0.88).
Han's analysis found a pooled relative risk of 0.87 for cardiovascular death per 1-MET higher fitness (95% CI 0.83 to 0.91). Compared with the lowest fitness, intermediate fitness had a summary relative risk of 0.67 for death from any cause (95% CI 0.61 to 0.74). The cancer estimates from the same paper are not reported on this page.
Lang and colleagues (2024) gathered earlier meta-analyses into one overview. In general populations, high versus low fitness went with a hazard ratio of 0.47 for death from any cause (95% CI 0.39 to 0.56). In people living with cardiovascular disease, the hazard ratio for cardiovascular death was 0.27 (95% CI 0.16 to 0.48).
A treadmill cohort, and the limits
Mandsager and colleagues (2018) followed patients referred for treadmill testing and grouped them by fitness relative to others of the same age and sex. Risk-adjusted death from any cause fell as fitness rose and was lowest in the elite group, defined as 2 or more SDs above the mean for age and sex. The authors saw no upper limit of benefit within their data. That is a finding about measured fitness in this cohort, not evidence that unlimited exercise is beneficial or safe.
Han and colleagues describe the current evidence as limited. All of these results are associations from observational data, and the Systematic assessment does not measure this treadmill-based fitness variable.
The evidence
Each cited source is labeled according to how it supports the particular claim on this page. Direct test evidence, underlying-capacity findings and population reference values are distinguished from Systematic-defined protocols and standards. Historical development notes are retained internally rather than presented as public evidence. A study of an underlying capacity is never presented as validation of the Systematic test itself.
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Underlying-capacity evidence New source
Han et al. (2022). Cardiorespiratory fitness and mortality from all causes, cardiovascular disease and cancer: dose-response meta-analysis of cohort studies. British journal of sports medicine.
What it found. Across 34 cohort studies, each 1-MET higher fitness level went with a pooled relative risk of 0.87 for cardiovascular death, and intermediate versus lowest fitness with 0.67 for death from any cause.
What it does not show. It does not show that changing fitness changes mortality, and the Systematic assessment does not measure this fitness variable.
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Underlying-capacity evidence New source
Kodama et al. (2009). Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis. JAMA.
What it found. Across 33 cohort studies (102980 participants and 6910 deaths from any cause), low fitness had a risk ratio for death from any cause of 1.40 versus intermediate and 1.70 versus high fitness.
What it does not show. An association per MET is not a guaranteed effect of a particular amount of exercise, and the Systematic tests do not measure this MET-based variable.
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Underlying-capacity evidence New source
Mandsager et al. (2018). Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA network open.
What it found. Among patients referred for treadmill testing, risk-adjusted death from any cause fell as fitness rose and was lowest in the elite group, with no upper limit of benefit observed in these data.
What it does not show. It is a retrospective cohort of referred patients. It does not show that unlimited exercise is beneficial or safe.
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Underlying-capacity evidence New source
Lang et al. (2024). 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. British journal of sports medicine.
What it found. An overview of meta-analyses found high versus low fitness went with a hazard ratio of 0.47 for death from any cause in general populations, and 0.27 for cardiovascular death in people with cardiovascular disease.
What it does not show. Its 20.9 million figure counts observations, not necessarily distinct people, and the reviews it gathers may share cohorts, so they are not independent replications.
The Systematic Healthspan Assessment is a physical baseline. It is not a diagnosis, and it does not estimate a biological age, a disease risk or a lifespan.