For years, doctors have given women with atrial fibrillation an extra point on their stroke risk score simply for being female—a practice so ingrained that it often led to prescriptions for blood thinners earlier and more often than for men with the same health profile. But a new Tulane University study challenges this assumption, revealing that female sex is not a uniform stroke risk factor, and that the one-size-fits-all approach may be exposing younger women to unnecessary medication risks.
The study, published in JACC: Advances, analyzed approximately 950,000 AFib patients using TriNetX, a large anonymized electronic health record database, and matched male and female patients based on age, other health conditions, and anticoagulation treatment to make direct comparisons. The finding is significant because it could reshape how clinicians decide who needs blood thinners—medications that prevent clots and stroke but also increase risks of bruising, prolonged bleeding, and gastrointestinal bleeding.
AFib is the most common heart rhythm disorder, causing the heart to beat irregularly and substantially raising stroke risk. For decades, standard care has relied on a scoring system that assigns points for risk factors like age, heart failure, diabetes, prior stroke, vascular disease, and high blood pressure. Under this framework, women automatically received one point for their sex alone—a practice born from a troubling historical gap: women comprised only about one-third of AFib trial participants, leaving their true risk profile poorly understood.
The Tulane researchers discovered that stroke risk does not increase equally across all female patients. Among patients younger than 75, there was no significant difference in one-year stroke risk between men and women. However, among patients age 75 and older, women did have a modest but statistically significant increase in stroke risk compared with men. Specifically, in patients 75 and older with no additional risk factors beyond age, women experienced about one additional stroke per 629 patients compared to their male counterparts.
"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," said Dr. Amitabh C. Pandey, director of Cardiovascular Translational Research at Tulane University School of Medicine. This distinction matters enormously: it means that younger women with AFib may have been overexposed to blood thinner side effects without a corresponding benefit.
The findings support growing momentum around the CHA2DS2-VA score, a newer risk assessment framework that removes sex as a standalone risk factor and instead considers individual health circumstances. Han Feng, Ph.D., an assistant professor at Tulane, emphasized that "not all women with AFib have the same risk profile, and these decisions should be individualized."
The challenge now is implementation. Medical guidance remains inconsistent, and newer scoring systems have not yet been universally adopted. Researchers stress that the goal is not to undertreat patients who genuinely need stroke prevention, but to identify with greater precision who will actually benefit from anticoagulation therapy. As Pandey put it, the focus must shift toward "modern tools and approaches that can personalize risk profiles to individuals"—a reminder that even well-intentioned medical practices need regular re-examination in light of better evidence.