The overall rate of strokes is declining in the United States, but appears to be going down mostly in men, a new study finds.
“Our findings suggest that the decreases in rates of stroke over time are primarily driven by decreased stroke rates in men,” said lead researcher Dr. Tracy Madsen.
That makes doctors wonder why American women aren’t seeing the same benefits from stroke prevention.
“It may be that stroke prevention strategies are not as effective in women compared with men; for example, future research should investigate the possibility that stroke risk factors like elevated blood pressure, cholesterol and diabetes are more severe or are not controlled as well in women,” Madsen said.
Madsen is an assistant professor of emergency medicine at the Warren Alpert Medical School of Brown University, in Rhode Island.
“Stroke is a debilitating yet preventable condition, and future efforts should focus on stroke prevention in both women and men, as well as figuring out why rates of stroke in women did not decrease over this time period,” she added.
For the study, Madsen and her colleagues collected data on 1.3 million adults living in southwest Ohio and northern Kentucky between 1993 and 2010.
They looked at hospital, clinic and coroners’ records to identify how many people had a first stroke during four one-year time periods, spaced approximately five years apart.
Among more than 7,700 strokes, 57 percent were women, the researchers said.
The rate of strokes among men went from 263 strokes per 100,000 at the start of the study to 192 per 100,000 at the end of the study.
For women, however, the rate went from 217 strokes per 100,000 in 1993 to 198 per 100,000 in 2010. This is not a statistically significant decline, the researchers said.
“By 2010, the rates of stroke were similar between women and men, which is different from previous data showing that rates of stroke are typically higher in men,” Madsen said.
“We also found that the declining rates of stroke in men are primarily driven by a decrease in ischemic strokes, a specific type of stroke caused by a lack of blood flow to the brain as a result of blocked arteries or clots,” Madsen said.
The rates for hemorrhagic stroke, which is caused by bleeding in the brain, remained stable for both women and men, the study found.
The researchers also noted that women were about four years older than men at the time of their stroke.
Data from the U.S. Centers for Disease Control and Prevention show that stroke has dropped to the fifth leading cause of death for men, but remains the fourth leading cause of death for women.
A limitation of the study is that information on risk factors for stroke that are unique to or more common in women — such as migraine and the use of hormone replacement therapy — were not collected, the researchers said.
Dr. Richard Libman, vice chair of neurology at Long Island Jewish Medical Center in New Hyde Park, N.Y., called the study results “fascinating and yet disturbing.”
The risk of stroke has historically been lower in women than in men. This has been true, especially for women before menopause. But even after menopause, when women start to catch up in terms of risk, the risk of stroke has been less than that of men, Libman said.
“It’s great news that stroke risk has declined among men, but it’s a mystery why the same decline in risk has not been seen among women,” he said.
One explanation might be that women tend to have atypical symptoms of stroke compared with men. For example, women may be less likely to have weakness or paralysis than men, Libman said.
“This means that women may be less likely to be recognized as having a stroke, which leads to a failure of implementation of appropriate measures to reduce the risk of future stroke,” he said.
This is just one possible explanation, Libman said. “But clearly there is much work to be done in order to ensure that women derive the same benefits from stroke risk reduction as have men,” he said.
The report was published online Aug. 9 in the journal Neurology.
For more information on stroke, visit the American Stroke Association.