Prevalence of dementia in Japan: a systematic review.

Background/Aims: The actual prevalence of dementia in Japan as well as the changes in the prevalence are not well known. Therefore, we undertook a systematic review to collect evidence regarding the prevalence of dementia in Japan. Methods: For this systematic review, we searched 2 electronic databases to identify cross-sectional or repeated cross-sectional studies with data regarding the study population, study location, diagnostic criteria, and prevalence of dementia. Results: Twenty-one studies were selected from 782 references. Sixteen studies surveyed individuals living at home; of these, 5 studies also included hospitalized or institutionalized patients. Most of the studies were conducted using a two-phase survey (phase I: screening, phase II: diagnosis of dementia). The clinical diagnosis of dementia was made based on the guidelines of the Diagnostic and Statistical Manual of Mental Disorders (DSM) in a majority of the studies. The prevalence of all types of dementia ranged from 2.9 to 12.5% and has been gradually increasing over the past few years. Conclusion: The results of this systematic review suggest that the prevalence of dementia has recently increased. However, further well-designed studies taking into account factors that affect the prevalence of dementia are needed to clarify the actual prevalence.