An estimated 6.8 million Americans alive today have suffered a stroke, and a majority are women.
Although the biggest risk factors are shared between men and women – such as smoking, obesity, and high blood pressure or cholesterol – a subset of risks are either exclusive to women or more likely to occur in women.
For the first time, stroke prevention guidelines have been developed by the American Heart Association / American Stroke Association to address these risk factors.
The sex-specific guidelines, published February in the AHA journal Stroke, are geared chiefly toward primary-care providers. They suggest prevention strategies and indicate the need for further research regarding the added risk factors linked to pregnancy, migraines with aura, birth control, atrial fibrillation, depression and hormone therapy, among others.
“Now we’re recognizing out that there are huge sex differences, not just in neurology, but in all of medicine…Women and men may need different prevention strategies, although 90 percent of them are the same,” said guideline co-author Louise McCullough, a professor of neurology and neuroscience at the University of Connecticut Health Center.
The guidelines spend considerable time on the hormone-related risk factors, but their biggest headline may be the role that simple longevity plays in women’s increased risk for stroke.
“Because women tend to live longer, their lifetime risk of stroke is higher than men. But on an age-by-age basis, a 50-year-old man is more likely to have a stroke — not by a lot, but some — than a woman,” said Dr. Sachin Rastogi, an interventional neuroradiologist at Mount Sinai Medical Center’s comprehensive stroke center in Miami Beach.
He thinks one of the most valuable things the new guidelines do is pick up on the under-diagnosis and under-treatment of atrial fibrillation, the most common type of arrhythmia (irregular heartbeat), especially in elderly women.
A-fib, as it is commonly called, increases the risk for ischemic stroke, which is caused by a blockage, such as a clot, that impedes blood flow to the brain. They account for about 87 percent of all strokes, and are linked to higher death and disability. While there are about the same number of men and women with A-fib overall, the risk of stroke because of A-fib increases with age, and older patients with AF are more likely to be women.
A-fib is “actually one of the more common causes of stroke that we actually intervene on in patients, and often it’s undiagnosed or diagnosed but inadequately treated,” Rastogi said.
The guidelines recommend better and more frequent screening for A-fib, and that when diagnosed in a patient with certain other risk factors, that blood thinners be prescribed.
The guidelines also note that the effect of strokes – from A-fib or otherwise – tend to have more severe consequences for women. Largely because women tend to have strokes later, they tend to be more disabling, and because women are more likely to have outlived their partners and to live alone, a stroke is more likely to lead to an expensive institutionalization.
The guidelines also elaborate on the increased risk of stroke borne of hypertensive disorders of pregnancy, and preeclampsia in particular. They note that preeclampsia not only carries an increased risk of stroke during pregnancy, but even decades after delivery.
The guidelines recommend that women of childbearing age with a history of high blood pressure be considered for low-dose aspirin to lower preeclampsia risks. They also recommend that pregnant women with moderately high blood pressure be considered for treatment, and that pregnant women with high blood pressure be treated. They also advise that preeclampsia be better recognized – and publicized – as an important risk factor for strokes even later in life.
According to McCullough, questions about preeclampsia are “not something that would typically be part of the history in an internal doctor’s appointment for a 60-year-old woman,” something she says needs to change.
The guidelines also note that hormone therapy, recently advertised to post-menopausal women as something which might reduce the risk of stroke, may in fact do just the opposite and increase that very risk.
They also reiterate that women need to be consistently screened for high blood pressure before being prescribed birth control pills, and that smoking as well as other risk factors (especially migraine with aura) may act synergistically with hormonal birth control to increase the likeliness of stroke.
The increased risk for stroke linked to depression is also noted – as is the marked lack of research elucidating the connection between the two.
McCullough emphasizes that “we still have a lot to learn about unique risk factors in women,” and the guidelines repeatedly indicate current research gaps that will need to be filled if a reliable female-specific score for stroke risk is to be developed.