Researchers have developed new peak heart rate calculations for exercise stress tests to account for differences in men’s and women’s cardiac performance over time.
“The standard that’s currently in use is somewhat outdated,” Thomas Allison, PhD, program director of the sports cardiology clinic at the Mayo Clinic in Rochester, Minnesota, said in a statement. “Every so often, you need to recalibrate what’s considered normal.”
An exercise stress test is a common diagnostic tool physicians use to diagnose conditions such as coronary heart disease, heart valve disease, and heart failure. The peak heart rate formula, calculated by subtracting age from 220, indicates the maximum heartbeats per minute a person should reach while exercising on a treadmill. Some people also use the formula to set their heart rate target during a workout.
Over time, however, researchers have realized the formula has limitations. “An equation developed 40 years ago based on a group that was predominantly men might not be accurate when applied to women today,” Allison said.
So Allison and his colleagues analyzed data from 25 000 patients who took stress tests at the Mayo Clinic between 1993 and 2006. The sample included men and women aged 40 to 89 years with no history of cardiovascular disease. Substantial differences between men and women emerged in their data.
Everyone’s peak heart rate decreases with age, but the data showed it declines more gradually among women than men. As a result, the currently used formula overestimates the peak heart rate that younger women can reach and underestimates it for older women.
The study, which Allison’s team will present at the American College of Cardiology Scientific Session that begins Saturday in Washington, DC, indicates that a more accurate way to calculate a woman’s peak heart rate is by subtracting 67% of her age from 200. The method applies to women aged 40 to 89 years because too few stress test results from women younger than 40 years were available to include in the data. For a man, a more accurate formula is subtracting 93% of his age from 216.
For a 50-year-old woman, the new formula gives a peak heart rate of 166 beats per minute, compared with 170 using the old formula. A 50-year-old man’s peak rate would drop by only 1 beat per minute, to 169, with the new formula.
The study also showed that men’s heart rates rise more dramatically during exercise and return to preexercise rates afterward more quickly than women’s. Allison and his colleagues didn’t examine potential physiological reasons for the differences, but they suggested that hormones, especially testosterone, may play a role.
Other researchers have suggested peak heart rate updates, but Allison and his colleagues said their study examined a larger sample size than previous studies and it’s the first to include data from women and men.