You might want to opt out of the treadmill portion of your next stress test if you’re a woman – the results might not be accurate.
While the stress tests have been used for years to determine a patient’s risk for cardiovascular disease, the scoring system was developed based on experiments done only with middle-aged men. Because of this criteria, a recent study suggests the data received from the tests for women could be skewed.
“There has been no good data to support its use in women,” said senior study author Leslie Cho, director of the Women’s Cardiovascular Center at the Cleveland Clinic in Ohio, by email to Reuters. “The score was likely underestimating risk for some women, while overestimating it for others, based on their age.”
The study looked at almost 110,000 patients’ sex-specific scores for risk of cardiovascular disease. Exercise capacity had the greatest effect on prognosis in both sexes and all risk factors had a differential effect on prognosis in women compared with men, the study said.
“Risk assessment tools for exercise treadmill testing may have limited external validity,” the study said. “Cardiovascular mortality has decreased in recent decades and women have been underrepresented in prior [studies].”
Scores from the commonly used Duke Treadmill Test focused primarily on exercise ability and didn’t account for health issues such as diabetes or high blood pressure – both of which can influence the risk of developing cardiovascular disease, Cho said.
Of the 60,000 patients seen at Cleveland Clinic, half were at least 54 years old and ages ranged from 45 to 63 years old. Almost 60 percent of the participants were men who generally had a higher exercise capacity along with higher odds of a history of coronary artery disease.
“It’s not so much that their risk factors are different but that an important component of the exercise treadmill testing is the exercise capacity which tends to be greater in men than women,” said Armin Zadeh, a researcher at Johns Hopkins University in Baltimore, who wasn’t involved with the study. “Therefore, the old criteria set an unfairly high bar for women to clear for the same prognostic value.”
When researchers developed sex-specific risk scores, they found a history of diabetes was associated with mortality in women. A history of heart failure and hypertension were associated with mortality in men.
Zadeh said looking at women separately can give a better idea of how well women perform on exercise tests based on what would be considered a good or bad performance for their female peers.
“When not separating scores, women will be held to a higher standard, which will bias results,” he said.
The study concluded that sex-specific scores will help to better estimate mortality in patients undergoing exercise treadmill testing, while helping to identify patients at the highest residual risk in the present area.
Five percent of men died during the study period compared to three percent of women. For both sexes, death was associated with a number of factors, including older age, diabetes, high blood pressure and more.