While chronological age is one of the most reliable risk factors for death, the way your body functions — your physiological health – is even more reliable, say Cleveland Clinic researchers.

The researchers developed a formula called A-BEST (Age Based on Exercise Stress Testing) to assess how well people exercise. The formula is based on exercise capacity and how the heart responds to and recovers from exercise. They evaluated more than 126,000 people (average age 53.5 years) who underwent exercise stress tests.

More than half of study participants between age 50 and 60 were physiologically younger than their chronological age using the A-BEST formula. At a nine-year follow-up, nearly 10,000 of the study participants had died. After adjusting for age, gender, smoking, body mass index (BMI), and other health indicators, A-BEST was found to be a better predictor of survival than chronological age in both men and women. The research was published in the European Journal of Preventive Cardiology.