From Counting to Understanding: The Evolving Epidemiologic Approach to Dementia

The aging of populations has raised concerns over the impact of an aging population on the prevalence and incidence 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 general 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 between 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 there seems to be little overall difference for all forms of dementia combined. Because of their greater number, there are more women with dementia.