BBC News - Exercise 'significant role' in reducing risk of dementia, long-term study finds

I am Sorry, but I see nothing here except association.   Cause and effect is not clearly established just based on what is here, unless there is more.  For all we know the effect was the excercise and the Cause was longer life.   More information is needed to convince this sceptic. BBC News - Exercise 'significant role' in reducing risk of dementia, long-term study finds