Alzheimer's Disease

I believe that the number of people newly diagnosed with Alzheimer's Disease each year has been increasing at a substantial rate.

Is that because there are larger numbers of old people than there used to be?

Or is the rate of Alzheimer's Disease incidence itself is increasing? If this is the case, what is causing it?

I believe that some years ago, public health authorities started advising people to reduce the amount of fat in their diets and in particular the amount of saturated fat. Do the years in which that policy has been pushed on the public correspond to the years that the Alzheimer's rate has been increasing?