The results, which appeared in The American Journal of Clinical Nutrition, agree with a host of other studies tying sugary drinks to numerous untoward health effects, including heart attacks, obesity and diabetes, and prompting government moves, such as New York's ban on super-sized sodas.
Given the increased availability of soft drinks in Japan over the past several decades, researchers led by Hiroyasu Iso at Osaka University wanted to see if soda drinkers there had higher risks of heart disease and stroke.
"Soft drink intake is associated with higher risk of ischemic stroke for women," wrote Ito and his team, referring to a kind of stroke with plaque buildup in the arteries.
Nearly 40,000 people answered a dietary, health and lifestyle questionnaire, first in 1990 and then again in 1995 and 2000. They were split into four groups -- those who rarely drank soft drinks, those who had one to two cups a week, those who had three to four cups a week and those who had a soft drink nearly every day.
Soft drinks were considered sugar-sweetened sodas and juices, and not diet sodas or 100% fruit juices.
The researchers then tracked how many people developed heart disease or had a stroke from the beginning of the study period until 2008.
Out of 11,800 women who rarely had a soft drink, 205 -- or 1.7% -- went on to have an ischemic stroke. Of the 921 women who had a soft drink a day, 28, or 3%, had such a stroke.
The research team saw no link in men between soft drink consumption and stroke risk, possibly because men with early signs of cardiovascular disease might have cut down on their soda drinking.
Ito and his colleagues wrote that the increased risk among female soda drinkers might be explained by the beverages' effects on metabolism. High soft drink intake is tied to an increase in weight gain, blood sugar and fats, and hypertension, which in turn is linked to an increased risk of ischemic stroke.
"It makes sense, if (sugar sweetened beverages) increase the risk for obesity, diabetes, insulin resistance, inflammation, then it should, in fact, raise the risk for cardiovascular disease, and that's what we're seeing," said Adam Bernstein, a researcher at the Cleveland Clinic, who was not involved with the study.
The study did not find that soft drinkers had an increased risk of heart disease caused by clogged arteries, perhaps because the underlying metabolic problems tied to soft drinks are more of a risk factor for stroke than for heart disease in this group of people, the authors wrote.
The American Beverage Association, which represents soda and soft drink makers, said the study had little new information.
"This study does nothing to educate people about the real causes of heart disease or heart health issues," the association said in a statement. "There is nothing unique about soft drinks when it comes to heart disease, stroke or any other adverse health outcomes."
