People who suffered a stroke have double the risk of developing dementia, which has scientists calling for more investment in promoting the healthy lifestyles that reduce the chances of stroke.

The largest study of its kind from the University of Exeter Medical School analysed data on stroke and dementia risk from 3.2 million people across the world.

"We found that a history of stroke increases dementia risk by around 70 percent, and recent strokes more than doubled the risk," said Dr. Ilianna Lourida of the University of Exeter Medical School.  "Given how common both stroke and dementia are, this strong link is an important finding.  Improvements in stroke prevention and post-stroke care may therefore play a key role in dementia prevention."

The researchers found the link between stroke and dementia even after taking into account other dementia risk factors such as blood pressure, diabetes, and cardiovascular disease.  These findings give the strongest evidence to date that having a stroke significantly increases the risk of dementia.

According to the UN World Health Organisation (WHO), 15 million people have a stroke each year.  Meanwhile, around 50 million people around the world have dementia; that is expected to almost double ever 20 years, reaching 131 million by 2050.  Stroke characteristics such as the location and extent of brain damage may help to explain variation in dementia risk observed between studies, and there was some suggestion that dementia risk may be higher for men following stroke than for women.