Published online by Cambridge University Press: 31 July 2009
As prior chapters have discussed, dementia is a neurodegenerative syndrome that encompasses many different specific diseases. Alzheimer's disease (AD) is the most common cause of dementia, accounting for approximately 70% of dementia cases; vascular dementia (VaD) accounts for another 10–20%. To date, most epidemiologic research on dementia has examined prevalence, incidence and risk factors for either all-cause dementia or for AD. Therefore, in this chapter, we also will discuss primarily what is known about the epidemiology of all-cause dementia and AD, with reference to other specific dementias when data are available.
The impending public health crisis of dementia
The prevalence of all-cause dementia, as well as AD and VaD, increases with age. For AD alone, prevalence may be as high as 10% in adults over the age of 65 years and nearly 50% in adults over 85 (Evans et al., 1989). In 2000, there were approximately 4.5 million people in the USA with AD. It is estimated that this number will nearly triple to 13.2 million by 2050 (Hebert et al., 2003) (Fig. 9.1). This increase in the prevalence of AD over the next 50 years will primarily reflect increased life expectancy and the aging of adults who were born during the “baby boom” after World War II (1946–1964), who will make up an increasingly large proportion of our population.