Prevalence and incidence of clinically diagnosed Alzheimer's disease dementia from 1994 to 2012 in a population study.

INTRODUCTION: The trends in prevalence and incidence of Alzheimer's disease (AD) dementia remain uncertain. METHODS: A sample of 2794 participants with a clinical diagnosis for AD dementia were included. RESULTS: The 2010 census standardized prevalence of AD dementia was 14.5% (95% CI = 13.7-15.3), and annual incidence was 2.3% (1.7-2.9). Both prevalence and incidence showed substantial variation over time, but no secular trends. The prevalence of AD dementia did not change significantly from 14.6% (95% CI = 13.0, 16.2) in 1994-1997 to 14.7% (95% CI = 13.2, 16.2) in 2010-2012 (P = .84). The annual incidence of AD dementia was 2.8% (95% CI = 2.2, 3.2) in 1998-2000 and 2.2% (95% CI = 1.6, 2.8) in 2004-2006 (P = .20) and remained steady in 2010-2012. The prevalence and incidence among African Americans were approximately twice than those among European Americans. CONCLUSIONS: The prevalence and incidence of AD dementia showed substantial variation between 1994 and 2012, but no secular trend.