People who occasionally binge-drink may have a heightened long-term risk of suffering a stroke, even if they do not regularly drink heavily, a new study suggests.

Researchers have known that while moderate drinking seems to lower the risk of heart disease and stroke, regular, heavy alcohol consumption has the opposite effect. But the relationship between sporadic binge-drinking and stroke risk has been unclear.

In the new study, Finnish researchers found that of nearly 16,000 adults followed for a decade, those who said they sometimes binged on alcohol were more likely to suffer a first-time stroke than non-bingers — regardless of their overall drinking patterns.

Compared with people who said they never binged, those who did were 56 percent more likely to suffer an ischemic stroke over 10 years. Ischemic strokes, which are caused by a blood clot in the vessels supplying the brain, account of the large majority of stroke cases.

Binge-drinking was also linked to 39 percent higher risk of suffering any type of stroke.

Dr. Laura Sundell and colleagues at the National Public Health Institute in Helsinki report the findings in the journal Stroke.

Past research has linked binge-drinking to a higher risk of fatal heart disease, independent of a person's average alcohol intake. The current findings suggest that it may similarly elevate stroke risk, according to Sundell's team.

The study included 15,965 Finnish adults between the ages of 25 and 64. At the outset, they estimated how often and how much they typically drank; heavy drinking was defined as roughly 30 drinks per week for men and about 17 drinks per week for women.

A binge-drinking episode was defined as having six or more drinks at one sitting for men, and four or more drinks for women.

Over the next 10 years, the study participants suffered a total of 249 strokes. Overall, binge-drinkers were at increased risk, regardless of whether they were generally heavy drinkers, and regardless of a number of other risk factors — like older age, smoking and high blood pressure.

It's not entirely clear why binge-drinking itself raises stroke risk, the researchers say, but large doses of alcohol are known to have short-term cardiovascular effects that may help explain the finding. These include spikes in blood pressure, increased blood clotting and heart-rhythm disturbances.