Different types of stroke have diverse risk profiles in overweight or obese women

According to new research, women who are overweight or obese may have an increased risk of the most common kind of stroke, called ischemic stroke, but a decreased risk of a more often deadly stroke, called hemorrhagic stroke. The study is published in the September 7, 2016, online issue of Neurology®, the medical journal of the American Academy of Neurology.

Stroke is a leading cause of death and disability worldwide and the fifth leading cause of death in the United States.

"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," said study author Gillian Reeves, PhD, with the University of Oxford, United Kingdom. "Our findings add to the growing body of evidence that different types of stroke have different risk profiles."

Kathryn Rexrode, MD, MPH, with Brigham and Women's Hospital in Boston, who wrote an accompanying editorial, noted that the lower risk of hemorrhagic stroke did not mean that overweight and obese women had a reduced risk of stroke overall. "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," she said. "Obesity is a substantial stroke risk factor for all ages and even more alarming for young adults."

For the study, 1.3 million women in the United Kingdom with an average age of 57 were followed for 12 years, during which time 20,549 had a stroke. Among the 344,534 women with a healthy weight (BMI between 22.5 and 25), 0.7 percent (2,253) had an ischemic stroke and 0.5 percent (1,583) had a hemorrhagic stroke. Of the 228,274 obese women (BMI 30 or more), 1.0 percent (2,393) had an ischemic stroke and 0.4 percent (910) had a hemorrhagic stroke.

For every five-unit increase in BMI the risk of ischemic stroke increased by 21 percent. For hemorrhagic stroke, every five unit increase in BMI was associated with a 12 percent decrease in risk.

The researchers also combined results from previously published studies. The totality of the worldwide evidence confirmed that risks associated with excess weight are consistently greater for ischemic than for hemorrhagic stroke.