Professor Carol Brayne, from Cambridge University's Institute of Public Health, said Alzheimer's could be tackled simply by becoming more active:
Simply tackling physical inactivity, for example, will reduce levels of obesity, hypertension and diabetes, and prevent some people from developing dementia as well as allowing a healthier old age in general - it's a win-win situation.
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The bus was heading to Mombasa and the lorry was travelling in the opposite direction when they collided on Tuesday, say Kenyan police.
"Corbyn himself has said he was a 200-1 outsider for the Labour leadership in 2015 and look where that one went," the PM told supporters.
A father filmed himself killing his baby daughter and posted the video clips on Facebook, before committing suicide, Thai police have said.