Dementia risk is reduced by exercise, although it is not clear why, one academic has noted.
The University of Stirling's Professor June Andrews has said that evidence has shown that leading a sedentary lifestyle can increase dementia risk, although it is not clear what the mechanism is.
One theory is that exercise heightens blood flow to the brain, increasing the oxygen supply.
In addition, being listless and depressed could heighten the severity of dementia symptoms, or cause them to come on quicker.
"It is very complicated and we are just at the beginning of finding out what does make a difference. However, the strongest evidence is for exercise so that couch-potato time needs to be rationed," she said.
This follows research published in the Proceedings of the National Academy of Sciences which found that a 'road block' technique could be used to treat Alzheimer's disease.
Blocking a pathway through brain cells could prevent the meeting of two agents which lay the foundations for the condition.
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