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Having a stroke doubles dementia risk

A history of stroke increases risk by around 70%, and a recent stroke more than doubles the risk

Ingrid Torjesen

Friday, 31 August 2018

People who have had a stroke are around twice as likely to develop dementia, suggests a large meta-analysis* published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association.

The study builds on previous research which has established that there is a link between stroke and dementia, but has not quantified the degree to which stroke actually increased dementia risk.

To better understand the link, researchers analysed 36 studies where participants had a history of stroke, including data from 1.9 million people, plus 12 studies that looked at whether participants had a recent stroke over the study period, adding a further 1.3 million people.

The researchers found that people who have had a stroke are around twice as likely to develop dementia and that the link between stroke and dementia persisted even after other dementia risk factors such as blood pressure, diabetes and cardiovascular disease were taken into account.

Dr Ilianna Lourida, of the University of Exeter Medical School, which led the research, said: "We found that a history of stroke increases dementia risk by around 70%, and recent strokes more than doubled the risk. 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."

Further research is required to clarify whether factors such as ethnicity and education modify dementia risk following stroke, the researchers said. Most people who have a stroke do not go on to develop dementia, so further research is also needed to establish whether differences in post-stroke care and lifestyle can reduce the risk of dementia further.

Dr David Llewellyn, from the University of Exeter Medical School, said: "Around a third of dementia cases are thought to be potentially preventable, though this estimate does not take into account the risk associated with stroke. Our findings indicate that this figure could be even higher, and reinforce the importance of protecting the blood supply to the brain when attempting to reduce the global burden of dementia."

*Ku┼║ma E, Lourida I, Moore SF, et al. Stroke and dementia risk: A systematic review and meta-analysis. Alzheimer's & Dementia: The Journal of the Alzheimer's Association, 31 August 2018, DOI:10.1016/j.jalz.2018.06.3061

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