Women who are obese or overweight are at an increased risk of having ischemic stroke in which blood flow to the brain is blocked, according to a new research released Wednesday. However, the study also found that these women have reduced chances of getting hemorrhagic stroke wherein a weakened blood vessel in the brain bursts or leaks.

The study published in Neurology journal examined 1.3 million women in the United Kingdom. The average age of the participants was 57 and they were followed up for 12 years. Of these, 344,534 had a healthy body mass index, that is, between 22.5 and 25, and 228,274 fell in the obese category with BMI of 30 or more.

The findings showed that during the research period, 20,549 people suffered a stroke. In the healthy weight category, 0.7 percent (2,253) had an ischemic stroke and 0.5 percent (1,583) had a hemorrhagic stroke. And of 228,274 women in the obese group who had a stroke — 1.0 percent (2,393) had an ischemic stroke and 0.4 percent (910) had a hemorrhagic stroke.

The study found that for every five unit increase in BMI, ischemic stroke risk increased by 21 percent but the risk of hemorrhagic stroke decreased by 12 percent. After combining results from previous studies, the researchers found that the risks associated with excess weight are constantly greater for ischemic than for hemorrhagic stroke.

“We found that the risk of ischemic stroke, which is associated with a blockage of blood flow to the brain and is the most common stroke subtype, is increased in overweight and obese women. By contrast, the risk of hemorrhagic stroke, which is associated with bleeding into the brain, is decreased in overweight and obese women,” study author Gillian Reeves of the University of Oxford said in a statement. “Our findings add to the growing body of evidence that different types of stroke have different risk profiles.”

However, the reduced risk of hemorrhagic stroke does not mean that overweight and obese women had lower stroke risk, Kathryn Rexrode of Brigham and Women’s Hospital in Boston, Massachusetts, pointed out in an accompanying editorial.

“Higher body mass index, or BMI, was associated with increased risk of total stroke in every category and the number of ischemic strokes was higher than the number of hemorrhagic stroke in every category. So higher BMI was not associated with protection or reduced risk of total stroke,” Rexrode said. “Obesity is a substantial stroke risk factor for all ages and even more alarming for young adults.”

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