‘Physiological age’ a better predictor of survival than chronological age

Physiological age based on exercise performance is a better predictor of long-term survival than chronological age, according to a study of more than 126,000 patients at the Cleveland Clinic.

Lead author Serge C. Harb, whose team’s results were published in the European Journal of Preventive Cardiology Feb. 13, calls age “one of the most reliable risk factors for death.” But other variables, like a person’s physical fitness and heart rate recovery, might alter that estimate.

“The older you are, the greater your risk of dying,” he said in a release. “But we found that physiological health is an even better predictor. If you want to live longer, then exercise more.”

Harb and colleagues studied a cohort of 126,356 patients referred to the Cleveland Clinic for an exercise (electrocardiography, echocardiography or myocardial perfusion imaging) stress test between 1991 and 2015. Patients’ data from the tests, including their exercise capacity, heart rate response to exercise and heart rate recovery were pulled and used to calculate an A-BEST (Age Based on Exercise Stress Testing) score the authors considered an individual’s “physiological age.”

The A-BEST equation was based on three major components: a person’s exercise capacity, their chronotropic competence and their heart rate recovery. Harb et al. adjusted their results to account for gender and any medications that could affect a patient’s heart rate.

After a mean follow-up of 8.7 years, the authors found that more than half of patients between 50 and 60 years old—55 percent of men and 57 percent of women—were physiologically younger than their chronological age, as indicated by their A-BEST score.

Harb and co-authors reported higher metabolic equivalents of task and a higher chronotropic reserve index were associated with improved survival in the patient population, whereas abnormal heart rate recovery was associated with a 53 percent increased risk of mortality and higher A-BEST scores were associated with a 5 percent increased risk of death. A significant increase in the area under the curve was found when using A-BEST prediction models over chronological age (0.82 versus 0.79).

“Knowing your physiological age is good motivation to increase your exercise performance, which could translate into improved survival,” Harb said. “Telling a 45-year-old that their physiological age is 55 should be a wake-up call that they are losing years of life by being unfit. On the other hand, a 65-year-old with an A-BEST of 50 is likely to live longer than their peers.”

He said his team’s approach might be used in the future to better inform patients of their true cardiovascular risk, and suggested doctors use A-BEST to report the results of exercise stress testing to patients with an indication for heart abnormalities.

“Telling patients their estimated age based on exercise performance is a powerful estimate of longevity and easier to understand than providing results for the individual components of the examination,” he said.