The new findings should not be taken to mean that everyone should start drinking coffee to lower their stroke risk, as the medical literature has been somewhat mixed regarding the effects of coffee on cardiovascular risk.
Of 34,670 women aged 49 to 83, women who drank more than a cup of coffee each day had a 22% to 25% lower risk for stroke than women who drank less coffee.
Women who reported drinking anywhere from one to five or more cups of coffee a day showed similar benefits in stroke reduction. Drinking more coffee did not reduce stroke risk any further, the study showed.
Exactly what it is about coffee that may lower stroke risk is unknown. Coffee may reduce inflammation and help make the body more responsive to insulin, the study authors say. It may also be that women who don’t drink coffee were exposed to another unknown risk factor.
“Additional prospective studies on coffee consumption and stroke incidence as well as mechanistic studies investigating possible effects of coffee consumption on cardiovascular risk factors are warranted,” write study authors, who were led by Susanna C. Larsson, PhD, lead researcher in the division of nutritional epidemiology at the National Institute of Environmental Medicine of the Karolinska Institute in Stockholm, Sweden.
During 10-plus years of follow-up, there were 1,680 strokes, including 1, 310 ischemic strokes, which are caused by blocked blood flow to regions of the brain; 154 hemorrhagic strokes, which are caused by bleeding in the brain; 79 subarachnoid hemorrhages, which are caused by bleeding in the subarachnoid space of the brain, and 137 unspecified types of strokes.
Coffee drinking lowered women’s risk for total strokes and ischemic and subarachnoid hemorrhages, in particular, the study found. Coffee consumption did not affect hemorrhagic stroke risk, but this may be due to the low number of these strokes in the new study.
Coffee Does Not Raise Stroke Risk
“It is quite clear that coffee consumption at moderate to even high levels does not increase risk of stroke,” says Eric Rimm, ScD, an associate professor of medicine at Harvard Medical School in Boston.
Recent studies have suggested that there may be a modest increase in stroke risk in the hour after coffee is drunk because of increased heart rate and blood pressure.
“Over the long run, the modest benefits on insulin sensitivity, reduced risk of diabetes, and many other benefits that may be in the coffee bean suggest in the long term there is limited risk and maybe even benefit for risk of stroke,” he says.
Roger Bonomo, MD, director of stroke care at Lenox Hill Hospital in New York City, says that giving up coffee to protect your health is not a good idea.
“Eliminating coffee isn’t good for your health,” he says. "Keep your coffee habits at a steady state."
Lower Stroke Risk by Targeting High Blood Pressure
It is too early to say whether anyone should drink more or less coffee to lower their stroke risk, says Cathy A. Sila, MD, the George M. Humphrey II Professor of Neurology and the director of the Stroke & Cerebrovascular Center at the Neurological Institute Case Medical Center of Case Western Reserve University School of Medicine in Cleveland, Ohio.
There are things that we can do today that we know will lower stroke risk, she says.
“The single most important risk factor for all stroke is high blood pressure, and the vast majority of people either don’t know they have it or know that they do and it is still not being controlled,” she says. “Get your blood pressure measured and if it is elevated, put a plan in place to lower it.” This may include losing weight, reducing salt intake, or taking medication.
“This is the most powerful thing we can do to lower stroke risk,” she says.