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

Abstract

Objective: To examine and summarise evidence from meta-analyses of cohort studies that evaluated the predictive associations between baseline cardiorespiratory fitness (CRF) and health outcomes among adults.

Design: Overview of systematic reviews.

Data source: Five bibliographic databases were searched from January 2002 to March 2024.

Results: From the 9062 papers identified, we included 26 systematic reviews. We found eight meta-analyses that described five unique mortality outcomes among general populations. CRF had the largest risk reduction for all-cause mortality when comparing high versus low CRF (HR=0.47; 95% CI 0.39 to 0.56). A dose-response relationship for every 1-metabolic equivalent of task (MET) higher level of CRF was associated with a 11%-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 outcomes, nine meta-analyses described 12 unique outcomes. CRF was associated with the largest risk reduction in incident heart failure when comparing high versus low CRF (HR=0.31; 95% CI 0.19 to 0.49). A dose-response relationship for every 1-MET higher level of CRF was associated with a 18% reduction in heart failure (HR=0.82; 95% CI 0.79 to 0.84). Among those living with chronic conditions, nine meta-analyses described four unique outcomes in nine patient groups. CRF was associated with the largest risk reduction for cardiovascular mortality among those living with cardiovascular disease when comparing high versus low CRF (HR=0.27; 95% CI 0.16 to 0.48). The certainty of the evidence across all studies ranged from very low-to-moderate according to Grading of Recommendations, Assessment, Development and Evaluations.

Conclusion: We found consistent evidence that high CRF is strongly associated with lower risk for a variety of mortality and incident chronic conditions in general and clinical populations.

Keywords: Cardiovascular Diseases; Cohort Studies; Physical fitness; Review.

Figure 1

PRISMA flow chart depicting the number of papers identified, screened and included in the overview. *A list of excluded studies with reasons are provided in online supplemental appendix 2.

Figure 2

HRs for each mortality outcome in apparently healthy populations at baseline for high versus low CRF and per 1-MET increase in CRF. Estimates from Laukkanen (2022), Han (2022), Kodama (2009) and Aune (2020) were reported as RR, the remaining studies were reported as HR. Qui (2021) reported estimates from self-reported CRF. Kodama (2009) reported low versus high CRF which were inverted for this study. CRF, cardiorespiratory fitness; CVD, cardiovascular disease; eCRF, estimated non-exercise cardiorespiratory fitness; GRADE, Grading of Recommendations, Assessment, Development and Evaluations; MET, metabolic equivalent of task; NA, not applicable; NR, not reported; RR, relative risk.

Figure 3

HRs for each incident outcome in apparently healthy populations at baseline for high versus low CRF and per 1-MET increase in CRF. Note: Estimates from Cheng (2022), Aune (2021), Wang (2020), Xue (2020), Tarp (2019) and Kunutsor (2023) were reported as RR, the remaining studies were reported as HR. Kandola (2019) reported estimates for low versus high which were inverted for this study. The estimates from Tarp (2019) are fully adjusted for adiposity. Aune (2021) was reported per 5-MET increase which we converted to 1-MET increase for this study. CRF, cardiorespiratory fitness; CVD, cardiovascular disease; GRADE, Grading of Recommendations, Assessment, Development and Evaluations; MET, metabolic equivalent of task; NA, not applicable; NR, not reported; RR, relative risk.

Figure 4

HRs for health outcomes in patients living with chronic conditions at baseline for high versus low CRF and delayed versus not delayed HRR. Estimates from Morris (2014) were reported as RR, the remaining estimates were reported as HR. Yang (2023), Fuentes-Abolafio (2020), Morris (2014), Rocha (2022) and Lachman (2018) reported estimates as low versus high which were inverted for this study. Cantone (2023) was reported per 1-unit VO₂ increase which we converted to 1-MET increase for this study. Adverse events for Lachman (2018) were all-cause mortality, cardiovascular mortality and hospitalisations for congestive heart failure. CRF, cardiorespiratory fitness; CVD, cardiovascular disease; GRADE, Grading of Recommendations, Assessment, Development and Evaluations; HRR, heart rate recovery; MET, metabolic equivalent of task; NA, not applicable; NR, not reported; RR, relative risk.