NYTimes story here.
The studies assessed dementia, which includes Alzheimer’s disease but also other conditions that can make mental functioning deteriorate. Richard Suzman, the director of the division of behavioral and social research at the National Institute on Aging, said it was not possible to know from the new studies whether Alzheimer’s was becoming more or less prevalent.
"dementia" is a syndrome (a collection of symptoms) not a disease, and has many causes.
One cause is "multi infarct dementia" caused by repeated ministrokes.
Treating high blood pressure and lowering cholesterol (which forms plaques that block the arteries) will decrease the rate of dementia.
And these medicines to lower blood pressure
have been available starting in the 1970's and for cholesterol in the 1990's....
so what about Alzheimer's disease?
That too might have several causes, and until they figure out the cause, treating it might not help.
Two factoids here: A lot of studies stress checking for "dementia" ignore the non alzheimer's causes, since we only check for symptoms, not pathology (cell changes).
Two: People with Down's syndrome (aka Mongolism, aka Trisomy 23) develop Alzheimer's disease in their 40's...they also are more prone to have certain forms of leukemia and hypo thyroidism (low thyroid function).
I remember when they transferred a Down's syndrome client to the "baby" (mainly bed ridden) ward where I was the doc when I worked in an ICF/MR (intermediate care institution/mental retardation).
When reviewing the chart, I saw a weight gain, and one nurse noted that he used to be a "terror" but now just sat around. Sure enough, his thyroid was almost zero...but the symptoms had come on so slowly that no one thought to check...(this was before the association was well known).