ABSTRACT
As background for the information in the chapters that follow, it is appropriate to review briefly the available English-language literature on the prevalence of dementia and its subtypes, with emphasis on the United States. As is the case with all topics included in this volume, available data on various populations have increased dramatically since they were reviewed in the first edition. Interpretation of this literature is difficult for many reasons; the most obvious reason is the lack of comparability between studies, because each uses different eligibility criteria, such as age, and different measures of dementia. Various screening instruments and various test batteries are used, some validated with the study populations and some not.
