Guest Editorial From Counting to Understanding: The Evolving Epidemiologic

The aging of populations has raised concerns over the im-pact of an aging population on the prevalence and inci-dence of age-associated diseases, such as the dementias. This demographic shift began earlier in Europe than elsewhere; during the 1980s, several epidemiologic studies recorded the prevalence and incidence of dementia in Europe (1–4). Other studies investigated US populations (5–7). By the early 1990s, comparative summaries had been written (8), and gen-eral consensus arose on several key findings. From age 65 to age 90 years, incidence and prevalence rates double with roughly every 5 years of age and then slow. The balance be-tween Alzheimer’s disease (AD) and vascular dementias may vary from place to place, but prevalence and incidence rates are comparable among countries when all forms of dementia are combined. Some studies showed different rates for men and women; however, this is far from consistent, and ther