The central finding of our projections of AD prevalence in the US population is that there will be substantial growth in the number of persons affected by the disease in the next 50 years because of increases in the oldest age groups of the population, in which the disease is most prevalent, unless we make substantial progress in prevention of this disease. Clearly, physicians may vary in judging the clinical condition most likely to be responsible for a person's dementia, and this variation may be especially evident in deciding whether such a person's illness is more attributable to vascular dementia or AD. Substantial variation also occurs in denoting the cut point used to decide whether a person has mild dementia. The essential idea is that although diagnostic variations do affect current AD prevalence estimates, the projected rapid growth in the number of persons with AD is driven more by the anticipated aging of the population. For example, Brookmeyer et al1 estimate current disease prevalence to be somewhat lower than we do but think that it will roughly quadruple in the next 50 years, whereas we estimate that it will approximately triple during this period.
Hebert LE, Bienias JL, Bennett DA, Evans DA, Scherr PA. Year 2000 Prevalence of Alzheimer Disease in the United States—Reply. Arch Neurol. 2004;61(5):803. doi:10.1001/archneur.61.5.803