Changes in cardiorespiratory fitness accurately predict mortality, study finds

An editorial called for more clinicians to use cardiorespiratory fitness as a key health indicator, based on this study of repeat treadmill testing among adults ages 30 to 95 years.

Changes in cardiorespiratory fitness (CRF) significantly affect mortality risk in those with and without cardiovascular disease (CVD), a study found.

Researchers assessed 93,060 participants ages 30 to 95 years with no evidence of overt cardiovascular disease at baseline using two symptom-limited exercise treadmill tests done one or more years apart. Participants were assigned to age-specific fitness quartiles based on peak metabolic equivalent of task score (METS) achieved on the baseline exercise treadmill test, and then by whether there was an increase, decrease, or no change in CRF on the final exercise treadmill test. Results were published by the Journal of the American College of Cardiology on March 20.

During a median follow-up of 6.3 years, 18,302 participants died, with an average yearly mortality rate of 27.6 events per 1,000 person-years. CRF remained unchanged in 25.1% of the participants, increased in 29.3%, and decreased in 45.6%. In general, changes in CRF of 1.0 MET or greater were associated with inverse and proportionate changes in mortality risk regardless of baseline CRF status. For example, in individuals with low fitness but no CVD, a decline in CRF of greater than 2.0 METS was associated with a 74% increase in mortality risk (hazard ratio, 1.74; 95% CI, 1.59 to 1.91).

The study authors noted that the impact of relatively small CRF changes on mortality risk has considerable clinical and public health significance. “The salient and unique finding of the current study is that it quantifies the volume of change in CRF needed to alter mortality risk,” they wrote. “These findings provide a guide for clinicians and the public in general regarding CRF changes necessary to improve CRF and health outcomes. Accordingly, encouraging the public to improve CRF by at least 1.0 MET can have considerable clinical and public health significance.”

An editorial said that CRF remains a vastly undervalued measure in both clinical settings and for public health. “We (again) call on both clinicians and public health professionals to adopt CRF as a key health indicator. This should be done by coupling routine assessments of CRF with continued advocacy for promoting [physical activity] as an essential healthy lifestyle behavior,” the editorialists wrote.