The medical community all but threw a party for itself when it recently announced that strokes had declined by nearly 40 percent in the last two decades. A recent study threw cold water on that, showing that only about half of us should be celebrating.
The study, published in the September 2017 issue of Neurology, analyzed data on 1.3 million men and women in Ohio and Kentucky from 1993 to 2010 and found that the decrease in stroke over time was primarily driven by a decrease in ischemic stroke in men.
“It was fairly surprising that, when you look at statistical significance, the decline in women between 1993 and 2010 was not significant whereas in men it was,” said Dr. Tracy Madsen, lead study author and assistant professor of emergency medicine at Brown University.
The age-adjusted study challenges the long-held assumption that stroke prevalence is higher in women than men due to their longer life expectancy, a major risk factor of strokes.
“I think that [age] is an oversimplification of the sex differences in stroke epidemiology,” Madsen said. “Even after we adjusted for age, the rates were still declining to a lesser extent in women than men.”
The study is the first to show significant sex differences in stroke incidence over time, and some experts warn it may be too early to draw concrete conclusions.
“Papers like this do highlight the differences between the two sexes, and I do think there’s something real there,” said Dr. Emer McGrath, a neurologist at Massachusetts General Hospital not affiliated with the study. “At the same time, I think it needs to be replicated and validated in another study before we necessarily say it’s true.”
The study joins a growing body of recent evidence on gender disparities in stroke. Studies show woman have more atypical stroke symptoms—such as body pain, migraine, and confusion—and are less likely to be prescribed statins, “a cornerstone of stroke prevention,” Madsen said. Plus, they have worse post-stroke outcomes than men—things Madsen witnessed first-hand as an emergency medicine physician.
“I was seeing a lot of women come in with either atypical symptoms or maybe with delayed presentations, like they had had symptoms for a day or two and decided not to seek care right away,” Madsen said. “Seeing these patients end up with fairly poor outcomes and residual deficits got me thinking about what the differences [by sex] were.”
Madsen found that while the evidence of sex differences in stroke was mounting, so were the gaps in research.
“There’s a lot more literature on cardiovascular disease in women than there is on stroke,” Madsen said. “I thought this was an area of need to really catch the research up so we had a better idea of what stroke looked like in women and how to improve outcomes.”
Madsen teamed up with researchers of the Greater Cincinnati/Northern Kentucky Stroke Study, an ongoing prospective study that since 1998 has analyzed stroke rates by race, but not specifically sex.
“Not that they weren’t reporting on sex and gender in their other studies, they just didn’t have someone in their group who wanted to look primarily at sex and gender,” Madsen said. “That’s kind of where I came in.”
Experts say the study results could have profound implications on preventative efforts for stroke in women.
“We need to see what’s working and what’s not working and try to understand how we can do better to prevent this disease,” said Dr. Hugo Javier Aparicio, a stroke neurologist at Boston Medical Center. “Stroke is very devastating and has a high mortality rate, so it’s important to stop these things before they happen.”
Currently, Madsen and her collaborators are analyzing data through 2015 to repeat the study, this time with an added age-stratified analysis to see whether the results are only true across certain age groups.
“It definitely takes some time to confirm that all cases are stroke and to ensure that all the data are correct before it’s ready for analysis,” Madsen said. “It’s a very rigorous study.”
For many women, the clock is ticking. Stroke will kill 55,000 more women than men in 2017, according to the CDC, and it won’t wait for the research to catch up.