New algorithm gauges mortality risk based on treadmill performance
Researchers have developed the FIT Treadmill Score, which can translate basic treadmill performance measures into a fitness-related mortality risk score.
A retrospective cohort study included 58,020 adults aged 18 to 96 years free from known CVD who were referred for an exercise stress test between 1991 and May 2009 (median age, 53 years; 49% women). Researchers collected demographic, clinical, exercise and mortality data to identify exercise test variables most predictive of survival. The beta coefficients of the model with the highest survival discrimination were used to construct the FIT Treadmill Score.
Haitham M. Ahmed
“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,” Haitham M. Ahmed, MD, MPH, cardiology fellow at the Johns Hopkins University School of Medicine, said in a press release. “We believe that our FIT score reflects the complex nature of [CV] health and can offer important insights to both clinicians and patients.”
According to the researchers, during a median 10-year follow-up, 11% of participants died. Ahmed and colleagues found that after age and sex, the most highly predictable variables of survival were peak metabolic equivalents of task and percentage of maximum predicted heart rate achieved (P < .001). The addition of baseline BP, baseline heart rate, change in vital signs, double product and risk factor data did not further improve survival discrimination, the researchers wrote.
The FIT Treadmill Score is calculated as [percentage of maximum predicted heart rate + 12(metabolic equivalents of task) – 4(age) + 43 (if female)]. Across the cohort, scores ranged from –200 (high risk for mortality) to 200 (low risk for mortality) in 98.1% of patients, distribution was near normal, and the Harrell C-statistic (0.811) indicated strong prediction of 10-year survival.
Michael J. Blaha
The percent risks for death during the next 10 years were as follows: 2% for those with a score of 100 or higher, 3% for a score of 0 to 100, 11% for a score of –100 to 0, and 38% for a score less than –100.
“The FIT Treadmill Score is easy to calculate and costs nothing beyond the cost of the treadmill test itself,” Michael J. Blaha, MD, MPH, director of clinical research at the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease, said in the press release. “We hope the score will become a mainstay in cardiologists’ and primary clinicians’ offices as a meaningful way to illustrate risk among those who undergo cardiac stress testing and propel people with poor results to become more physically active.” – by Erik Swain
Disclosure: The researchers report no relevant financial disclosures.
Editor’s note: On March 9, this article was updated to correctly describe the FIT Treadmill Score as incorporating metabolic equivalents of task. The Editors regret this error.