State of Physical Fitness is a Reliable Predictor of Age-Related Mortality
Being more physically fit at a given age reliably correlates with a lower future mortality risk. While human epidemiological data can only provide correlations, animal studies can and do provide evidence for physical fitness and exercise to modestly slow aspects of aging and reduce age-related mortality. In general, maintaining physical fitness into later life appears to be a good idea, based on the evidence.
Cardiorespiratory fitness (CRF) is a physical trait that reflects the integrated function of numerous bodily systems to deliver and use oxygen to support muscle activity during sustained, rhythmic, whole-body, large muscle physical activity. CRF can be objectively measured using direct (usually by maximal exercise testing with concomitant gas exchange analysis) or indirect (exercise predicted equations) methods with a variety of maximal or submaximal protocols.
Low CRF is considered a strong chronic disease risk factor that is not routinely assessed in clinical practice. Evidence suggests that the inclusion of CRF as a clinical vital sign would enhance patient management by improving the classification of those at high risk of adverse outcomes. The evidence supporting CRF as an important risk factor has accumulated since the 1980s through large cohort studies that investigated the prospective risk of all-cause mortality and cardiovascular events associated with CRF. Research has linked CRF to the incidence of some cancers, type 2 diabetes, metabolic syndrome, stroke, and depression. Higher CRF may even improve the prognosis in those with chronic conditions such as cancer, peripheral artery disease, heart failure, and chronic kidney disease.
The objective of this study was to conduct an overview of systematic reviews with meta-analyses from cohort studies that investigated relationships between CRF and prospective health-related outcomes among adults. We identified 26 systematic reviews with meta-analysis representing over 20.9 million observations from 199 unique cohort studies. CRF had the largest risk reduction for all-cause mortality when comparing high versus low CRF (hazard ratio, HR=0.47). 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). The certainty of the evidence across all studies ranged from very low-to-moderate according to Grading of Recommendations, Assessment, Development and Evaluations.