Researchers here provide evidence to demonstrate that fairly standard exercise stress tests are better at predicting mortality in older individuals than chronological age. People age at different paces, and some portion of this variation is the secondary aging of lifestyle choices such as diet and physical activity or inactivity. The challenge with human studies of activity and aging is that they can really only provide evidence of correlation rather than causation. The animal studies are fairly compelling on causation when it comes to exercise and a lower rate of mortality in late life, however. It seems more plausible for humans to work much the same way than for there to be a major difference in the interaction between exercise and aging in humans versus other mammals.
Based on exercise stress testing performance, the researchers developed a formula to calculate how well people exercise - their "physiological age" - which they call A-BEST (Age Based on Exercise Stress Testing). The equation uses exercise capacity, how the heart responds to exercise (chronotropic competence), and how the heart rate recovers after exercise. "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."
The study included 126,356 patients referred between 1991 and 2015 for their first exercise stress test, a common examination for diagnosing heart problems. It involves walking on a treadmill, which gets progressively more difficult. During the test, exercise capacity, heart rate response to exercise, and heart rate recovery are all routinely measured. The data were used to calculate A-BEST, taking into account gender and use of medications that affect heart rate.
The average age of study participants was 53.5 years and 59% were men. More than half of patients aged 50-60 years - 55% of men and 57% of women - were physiologically younger according to A-BEST. After an average follow-up of 8.7 years, 9,929 (8%) participants had died. As expected, the individual components of A-BEST were each associated with mortality. Patients who died were ten years older than those who survived. But A-BEST was a significantly better predictor of survival than chronological age, even after adjusting for sex, smoking, body mass index, statin use, diabetes, hypertension, coronary artery disease, and end-stage kidney disease. This was true for the overall cohort and for both men and women when they were analysed separately.