Study: There’s no such thing as ‘too fit’
Having reduced cardiorespiratory fitness (CRF) is as harmful to survival as coronary artery disease, smoking cigarettes or diabetes, suggests a retrospective study published Oct. 19 in JAMA Network Open.
Researchers analyzed data from 122,007 patients who underwent exercise treadmill testing, and stratified those individuals into five CRF groups based on how they stacked up against the average person of their age and sex: low (below 25th percentile), below average (25th-49th percentile), above average (50th-74th percentile), high (75th-97.6th percentile) and elite (97.7th percentile or higher).
Elite performers were 80 percent less likely to die than low performers over the median follow-up of 8.4 years. They were even 23 percent more likely to survive than high performers, an important finding considering recent evidence has suggested extreme amounts of exercise might actually be harmful. In this study, there appeared to be no upper limit for the benefit of increased CRF.
“Potentially adverse cardiovascular findings in highly active cohorts, including an increased incidence of atrial fibrillation, coronary artery calcification, myocardial fibrosis, and aortic dilation, have raised concern for potential cardiovascular risk above a certain exercise or training threshold,” wrote lead author Kyle Mandsager, MD, of the Cleveland Clinic Foundation, and colleagues. “It remains unclear whether these associations are signals of true pathologic findings or rather benign features of cardiovascular adaptation. The present study is the first, to our knowledge, to specifically evaluate the association between extremely high CRF and long-term mortality.”
The researchers noted their study is also different from many previous reports because it uses an objective measure of physical fitness rather than self-reported activity levels. Also, genetic factors and other lifestyle habits may contribute to both aerobic fitness and improved survival, they wrote.
Upon multivariable adjustment, Mandsager et al. found participants with below-average CRF versus above-average CRF had 41 percent decreased odds of survival—a risk on par with smoking or diabetes, and even greater than coronary artery disease (29 percent increased risk of all-cause mortality). And the survival odds were even greater for people with CRFs categorized as high or elite for their age and sex.
“These findings not only reinforce the large collective body of evidence correlating aerobic fitness with numerous health benefits but also illustrate the importance of aerobic fitness as a powerful, modifiable indicator of long-term mortality,” the authors wrote. “Healthcare professionals should encourage patients to achieve and maintain high levels of fitness.”
Daniel joined TriMed’s Chicago editorial team in 2017 as a Cardiovascular Business writer. He previously worked as a writer for daily newspapers in North Dakota and Indiana.