Cardiologists who have developed a new formula to predict the likelihood of death based on a treadmill test, say fitness was the single most powerful indicator of death and survival, trumping important variables such as diabetes and family history.

Researchers from the Johns Hopkins Medicine (JHM) institution in Baltimore, US, say their formula can predict a person's risk of dying over the next decade, based on their ability to exercise on a treadmill at an increasing speed and incline.

For their research – outlined in the latest edition of the journal Mayo Clinic Proceedings – the cardiologists studied data on 58,020 people, aged 18 to 96, who underwent standard exercise stress tests for evaluation of chest pain, shortness of breath, fainting or dizziness. The researchers then tracked how many of the participants within each fitness level died from any cause over the next decade.

The results reveal that among people of the same age and gender, fitness levels as measured by METs (also known as metabolic equivalents – a gauge of how much energy the body expends during exercise) and peak heart rate reached during exercise were the greatest indicators of death risk.

"The notion that being in good physical shape portends lower death risk is by no means new, but we wanted to quantify that risk precisely by age, gender and fitness level, and do so with an elegantly simple equation that requires no additional fancy testing beyond the standard stress test," said lead investigator Haitham Ahmed.

"Stress test results are currently interpreted as 'either/or' but we know that heart disease is a spectrum disorder. We believe that our FIT score reflects the complex nature of cardiovascular health and can offer important insights to both clinicians and patients."

Under the new algorithm, dubbed the FIT Treadmill Score, people are scored between -200 to 200, with that figure corresponding to a risk of death over the next decade. Patients who score 100 or higher have a 2 per cent risk of dying over the next 10 years, while those with scores between -100 and 0 face an 11 per cent death risk over the next decade. In other words, two of 100 people of the same age and gender with a score of 100 or higher would die over the next decade, compared with 11 out of 100 for those with a fitness score between -100 and 0.

Published along with the study is a chart depicting death risk by age, gender and fitness level, which can be printed on placards for use in doctor’s offices to guide clinical advice.

"The FIT Treadmill Score is easy to calculate and costs nothing beyond the cost of the treadmill test itself," said senior study author Michael Blaha. "We hope that illustrating risk that way could become a catalyst for patients to increase exercise and improve cardiovascular fitness.”

Given that many people are encouraged to seek a stress test from doctors before joining health clubs or embarking on exercise regimes, the test has potential implications for gyms in terms of boosting motivation and quantifying exercise improvements. For example, those with a high risk of death in the next decade could be shown how that risk diminishes as their fitness levels improve.