For many years, doctors have believed that women with atrial fibrillation, often called AFib, automatically face a higher risk of stroke than men.
This belief has influenced treatment decisions around the world and has been built into commonly used medical guidelines.
However, a large new study from Tulane University is now challenging that long-standing assumption and suggesting that the relationship between sex and stroke risk may be more complex than previously thought.
Atrial fibrillation is the most common heart rhythm disorder. It occurs when the upper chambers of the heart beat irregularly and out of sync with the lower chambers. This abnormal rhythm can cause blood to pool inside the heart, increasing the risk of blood clots.
If a clot travels to the brain, it can block blood flow and cause a stroke. Because strokes can lead to disability or death, preventing them is one of the most important goals in AFib treatment.
To reduce stroke risk, many patients with AFib are prescribed anticoagulants, often called blood thinners. These medicines can be very effective at preventing clots, but they also carry risks.
Some people experience bruising, prolonged bleeding, stomach bleeding, or other serious complications. As a result, doctors try to carefully balance the benefits and risks before prescribing these medications.
For years, clinicians have used a scoring system to estimate stroke risk in AFib patients. This system assigns points for risk factors such as older age, high blood pressure, diabetes, heart failure, vascular disease, and previous stroke.
Women automatically receive an additional point simply because they are female. This often means women become eligible for blood-thinning medication earlier than men with otherwise similar health profiles.
Researchers at Tulane University wanted to take a closer look at whether female sex truly increases stroke risk in all women with AFib. Their findings were published in JACC: Advances.
The research team analyzed data from nearly 950,000 patients using TriNetX, a large electronic health records database. They compared men and women across three age groups: younger than 65, between 65 and 74, and 75 years of age or older.
To make comparisons as fair as possible, researchers matched patients based on age, medical conditions, and whether they were receiving anticoagulant treatment.
The results revealed an important pattern. Among patients younger than 75 years old, researchers found no meaningful difference in stroke risk between men and women. This suggests that being female alone may not significantly increase stroke risk in most younger AFib patients.
However, the picture changed among people aged 75 and older. In this age group, women experienced a modest but statistically significant increase in stroke risk compared with men. Even then, the increase was relatively small.
Among older patients who had no additional risk factors besides age, the researchers estimated that there was approximately one extra stroke for every 629 women compared with men.
The findings suggest that female sex may be better understood as a risk modifier rather than a universal risk factor. In other words, being female appears to matter more in certain situations, particularly among older women and those with multiple health problems.
According to the researchers, these findings support growing interest in a newer risk assessment approach known as the CHA2DS2-VA score, which removes sex as an independent risk factor. Still, they emphasize that more research is needed before treatment guidelines are fully updated.
The study may have important implications for patient care. Instead of applying the same assumptions to all women with AFib, doctors may eventually be able to make more personalized decisions based on a person’s age, overall health, and individual risk profile.
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Source: Tulane University.
