Excess weight has different effects on different types of stroke

Women who are overweight or obese have an increased risk of the most common type of stroke, called ischaemic stroke, but a decreased risk of a more often fatal type of stroke, called haemorrhagic stroke. That's the conclusion of research from Oxford University's Cancer Epidemiology Unit.

Professor Gillian Reeves said: 'We found that the risk of ischaemic 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 haemorrhagic stroke, which is associated with bleeding into the brain, is decreased in overweight and obese women.

'Our findings add to the growing body of evidence that different types of stroke have different risk profiles.'

For the study, 1.3 million British women 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 ischaemic stroke and 0.5 percent (1,583) had a haemorrhagic stroke. Of the 228,274 obese women (BMI 30 or more), 1.0 percent (2,393) had an ischaemic stroke and 0.4 percent (910) had a haemorrhagic 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 team also combined their findings with those from twelve previously published studies and showed that adiposity associated risks are consistently greater for ischaemic than for haemorrhagic stroke.

The paper, Adiposity and ischaemic and hemorrhagic stroke, is published in Neurology (doi: 10.1212/WNL.0000000000003171).