[bill_from_tampa]

"People who exercise more are less likely to get dementia, possibly because it maintains blood flow to the brain. "

Or, perhaps, people who are able to exercise and have the drive and foresight to exercise regularly for years don't have early stages of dementia. Unless a study has been done that randomized persons at age 40-50 to 'exercise' and "no exercise" groups, and followed them for 30-40 years, this is a hard question to answer. Following groups of people who self-sort themselves into exercisers and non-exercisers does not answer this question, as the exerciser group may include less early-dementia persons (ie those 20-30 years from a clinical diagnosis, but who may be experiencing early behavioral changes that are not diagnostic).