The largest contributor to dementia's expansion is that, worldwide, people are living longer. When you have four times the number of people in the older age groups (projected for the middle of the century), you automatically will have four times the number of people with dementia unless we find something to stem the tide. Early diagnosis promotes the expansion somewhat, but not as much as the shifting population age structure. We no longer have a pyramid structure to the population, with fewer older adults relative to younger, but more of a rectangle with a burgeoning at the older ages.

It has been shown that if we could find something to delay AD dementia, we would have fewer cases. For example, even a delay of two years on average would reduce the U.S. burden of dementia by at least a couple of million people.

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