Are you drinking a cup of coffee right now? Congratulations, you may be lowering your risk of stroke, according to study of nearly 35,000 women published Thursday in Stroke: Journal of the American Heart Association.
The study led by Susanna Larsson of the Karolinska Institute in Stockholm followed women aged 49 to 83 for an average of 10 years, and found that those who drank more than one cup of coffee a day had a 22% to 25% lowered risk of stroke, compared with women who drank less. Further, the study found, drinking little or no coffee was actually associated with a slight increase in stroke risk.
“Some women have avoided consuming coffee because they have thought it is unhealthy,” said Larsson in a statement. “In fact, increasing evidence indicates that moderate coffee consumption may decrease the risk of some diseases such as diabetes, liver cancer and possibly stroke.”
Still, the authors say their findings are preliminary and shouldn’t change people’s coffee-drinking habits. The past medical literature on the impact of coffee on cardiovascular health has been mixed, but much data support the current findings. As USA Today‘s Janice Lloyd reported:
The results are consistent with findings on 83,076 women in the Nurses Health Study in the USA in 2009. In that study, women who drank four or more cups of coffee a day had a 20% reduced risk of stroke, compared with women who had less than one cup per month. That study distinguished between caffeinated and decaf; the decaf group had a slightly lower risk.
The women in the Swedish study were not asked whether they drank decaf or regular coffee, but most Swedes drink caffeinated coffee, Larsson noted. (More on Time.com: 5 Better-For-You Breakfasts)
The current study tracked participants of the Swedish Mammography Cohort, a long-term study focusing on the associations between diet, lifestyle and disease. Researchers collected data on women’s coffee consumption and incidence of stroke between 1998 and 2008. There were 1,680 cases of stroke during that time period, with a reduced risk among women who drank coffee. The amount of coffee women drank over and above one cup didn’t reduce risk further — that is, women who drank five or more cups had the same reduction in stroke risk as women who drank one to two cups, compared with those who drank less — and the association remained even after researchers took into account smoking, drinking, weight, diabetes and blood pressure.
Why coffee may lower stroke risk isn’t clear, but researchers speculated that it might reduce inflammation or improve insulin resistance, which may help lower risk for stroke. (More on Time.com: A Man Dies After Overdosing on Caffeine)
However, as other experts pointed out, it’s also not clear that stroke-risk reduction can be attributed to coffee. HealthDay reported:
The problem with this type of study is that there are too many factors unaccounted for and association does not prove causality, said Dr. Larry B. Goldstein, director of the Duke Stroke Center at Duke University Medical Center.
“Subjects were asked about their past coffee consumption in a questionnaire and then followed over time. There is no way to know if they changed their behavior,” Goldstein said.
And, he noted, there was no control for medication use or other potential but unmeasured factors.
The good news for caffeine junkies is that at least drinking coffee didn’t increase women’s risk of stroke.