Heavy drinkers may have a higher risk of stroke than those who drink moderately or not at all.

A study led by researchers at Beth Israel Deaconess Medical Center and the Harvard School of Public Health found that middle-aged and older men who consume more than two drinks a day over several years are more likely than nondrinkers to have an ischemic stroke, while those who drink moderately have the same or a slightly lower risk than teetotalers.

The report follows findings from the same large pool of men that those who drink moderately or not at all had a lower risk of heart disease and diabetes, said lead researcher Dr. Kenneth Mukamal, a Beth Israel internist and assistant professor at Harvard Medical School.

About 412 — or 1 percent — of the 38,156 male health professionals who returned questionnaires biennially over 14 years of the study reported having strokes (family members reported fatalities). The heavier drinkers had a relative stroke risk that was 20 percent to 40 percent higher than those who abstained.

It isn’t clear why excessive drinking may raise the risk of stroke. Mukamal said it may be because alcohol tends to raise blood pressure and adds to atrial fibrillation, in which blood isn’t properly pumped through the heart’s upper chambers.