Cardiorespiratory fitness emerged as a stronger predictor of all-cause mortality than did any traditional risk factor across the spectrum of age, sex, and race in a modeling study that included more than 750,000 U.S. veterans.
In addition, mortality risk was cut in half if individuals achieved a moderate cardiorespiratory fitness (CRF) level – that is, by meeting the current U.S. physical activity recommendations of 150 minutes per week, the authors note.
Furthermore, contrary to some previous research, “extremely high” fitness was not associated with an increased risk for mortality in the study, published online in the Journal of the American College of Cardiology.
“This study has been 15 years in the making,” lead author Peter Kokkinos, PhD, Rutgers University, New Brunswick, N.J., and the VA Medical Center, Washington, told this news organization. “We waited until we had the computer power and the right people to really assess this. We wanted to be very liberal in excluding patients we thought might contaminate the results, such as those with cardiovascular disease in the 6 months prior to a stress test.”
Figuring the time was right, the team analyzed data from the VA’s Exercise Testing and Health Outcomes Study (ETHOS) on individuals aged 30-95 years who underwent exercise treadmill tests between 1999 and 2020.
After exclusions, 750,302 individuals (from among 822,995) were included: 6.5% were women; 73.7% were White individuals; 19% were African American individuals; 4.7% were Hispanic individuals; and 2.1% were Native American, Asian, or Hawaiian individuals. Septuagenarians made up 14.7% of the cohort, and octogenarians made up 3.6%.
CRF categories for age and sex were determined by the peak metabolic equivalent of task (MET) achieved during the treadmill test. One MET is the energy spent at rest – that is the basal metabolic rate.
Although some physicians may resist putting patients through a stress test, “the amount of information we get from it is incredible,” Dr. Kokkinos noted. “We get blood pressure, we get heart rate, we get a response if you’re not doing exercise. This tells us a lot more than having you sit around so we can measure resting heart rate and blood pressure.”
Lowest mortality at 14.0 METs
During a median follow-up of 10.2 years (7,803,861 person-years), 23% of participants died, for an average of 22.4 events per 1,000 person-years.
Higher exercise capacity was inversely related to mortality risk across the cohort and within each age category. Specifically, every 1 MET increase in exercise capacity yielded an adjusted hazard ratio for mortality of 0.86 (95% confidence interval, 0.85-0.87; P < .001) for the entire cohort and similar HRs by sex and race.
The mortality risk for the least-fit individuals (20th percentile) was fourfold higher than for extremely fit individuals (HR, 4.09; 95% CI, 3.90-4.20), with the lowest mortality risk at about 14.0 METs for both men (HR, 0.24; 95% CI, 0.23-0.25) and women (HR, 0.23; 95% CI, 0.17-0.29). Extremely high CRF did not increase the risk.
In addition, at 20 years of follow-up, about 80% of men and 95% of women in the highest CRF category (98th percentile) were alive vs. less than 40% of men and approximately 75% of women in the least fit CRF category.
“We know CRF declines by 1% per year after age 30,” Dr. Kokkinos said. “But the age-related decline is cut in half if you are fit, meaning that an expected 10% decline over a decade will be only a 5% decline if you stay active. We cannot stop or reverse the decline, but we can kind of put the brakes on, and that’s a reason for clinicians to continue to encourage fitness.”
Indeed, “improving CRF should be considered a target in CVD prevention, similar to improving lipids, blood sugar, blood pressure, and weight,” Carl J. Lavie, MD, Ochsner Health, New Orleans, and colleagues affirm in a related editorial.