New study reevaluates stroke risk for female patients with atrial fibrillation

A new Tulane University study challenges a long-standing assumption in heart care: that being female automatically increases stroke risk for patients with atrial fibrillation, a common condition that causes the heart to beat irregularly.

The study, published in JACC: Advances, found that stroke risk does not increase equally across all female patients with AFib. Instead, the study suggests that being female is more like a risk modifier, with increased stroke risk seen primarily among women age 75 and older or those with a greater burden of other health conditions.

AFib is the most common heart rhythm disorder and is associated with a higher risk of stroke, a condition often treated with blood thinners. The findings could shift thinking on how often women are prescribed blood thinners versus men who have otherwise similar risk profiles.

For years, female sex has been included as a risk factor along with other factors such as high blood pressure and diabetes, meaning women were more likely to be prescribed anticoagulants. Our study shows younger women may not have as much added stroke risk as previously thought, while older women, particularly those over 75, appear to have a higher risk that deserves close attention."

Dr. Amitabh C. Pandey, co-corresponding author, director of Cardiovascular Translational Research at Tulane University School of Medicine

Typically, to determine if AFib patients should be prescribed blood thinners, clinicians use a scoring system which assigns points for risk factors such as age, heart failure, diabetes, prior history of stroke, vascular disease and high blood pressure. Under that system, women receive one point for their sex alone.

This can result in female AFib patients being eligible for blood thinners earlier or more often than men. While these medications can help prevent clot-related strokes, they can also increase the risk of bruising, prolonged bleeding, gastrointestinal bleeding and other serious complications.

"This general approach came from women being underrepresented in AFib trials and studies comprising only about one-third of study populations," said co-corresponding author Han Feng, PhD, assistant professor at Tulane University School of Medicine. "Our study shows not all women with AFib have the same risk profile, and these decisions should be individualized."

Using TriNetX, a large anonymized electronic health record database, Tulane researchers analyzed approximately 950,000 patients with AFib and compared stroke outcomes between male and female patients across three age groups: younger than 65, 65 to 74, and 75 and older. Researchers matched male and female patients based on age, other health problems and whether they were prescribed anticoagulation medicine to allow for more direct comparisons.

Among patients younger than 75, the study found no significant difference in one-year stroke risk between men and women. However, among patients age 75 and older, women had a modest but statistically significant increase in stroke risk compared with men.

In patients 75 and older with no additional risk factors beyond age, women saw about one additional stroke per 629 patients compared to their male counterparts.

The findings support growing interest in the newer AFib risk score framework – called the CHA2DS2-VA score – which removes sex as a standalone risk factor. Still, researchers said additional studies are needed and medical guidance remains inconsistent.

"These findings highlight the need for modern tools and approaches that can personalize risk profiles to individuals," Pandey said. "The goal is not to under treat patients who need stroke prevention, but to better identify who is most likely to benefit from anticoagulation and who may be exposed to unnecessary risk."