Women with atrial fibrillation (AF) have a higher risk than men of suffering ischaemic stroke, research has shown. Authors of the study, published today on bmj.com, say this means that doctors should consider the sex of a patient with AF when making a decision about prescribing anticoagulants.
However, women under 65 with no other risk factors are still at low absolute risk, and do not need to take anticoagulation treatment.
Previous studies have been at odds over whether female sex itself is a risk factor for ischaemic stroke in people with AF, so researchers from Birmingham and Sweden conducted a large study to investigate this further.
They examined data on 100,802 people with AF being treated as in- or outpatients by hospitals in Sweden, followed for a median of 1.2 years. They excluded patients with warfarin use at baseline, mitral stenosis, previous valvular surgery, or who died within 14 days from baseline.
The risk of suffering an ischaemic stroke was low in absolute terms, but was 47% more common in women – who had an overall annual stroke rate of 6.2% – than in men, in whom the rate was 4.2%. Even after adjusting for 35 other relevant risk factors, women with AF were still 18% more likely than men to suffer an ischaemic stroke.
However, women younger than 65, whose only risk factor for stroke was AF, were not significantly more likely than men to have a stroke.
The authors of the study concluded: “Women with atrial fibrillation have a moderately increased risk of stroke compared with men, and thus, female sex should be considered when making decisions about anticoagulation treatment.
“However, women younger than 65 years and without other risk factors have a low risk for stroke, and do not need anticoagulant treatment.”
Professor Eva Prescott from the University Hospital, Bispebjerg in Denmark said in her accompanying editorial that, despite some inherent weaknesses, this and other registry studies can reassure clinicians: “The registry data confirm overall that women are at higher risk of stroke than men, but when differences in age and risk factor profile are taken into account the excess risk is low.
“More importantly, the absolute risk in younger women with no other risk factors is low and does not merit treatment with oral anticoagulants.”