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

Abstract

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.

Keywords: Dementia trends; Epidemiological study; Incidence; Prevalence.

Figure 1.. The CHAP Study Design and Clinical Evaluations Sample Selection between 1994 and 2012

The N in the study cohort shows the number eligible for the population interview to be selected for clinical evaluations. The N in the clinical evaluation shows the number of study participants with a clinical diagnosis for each triennial cycle. In CHAP study, a total of 4,021 clinical evaluations are performed on 2,794 participants between 1994 and 2012.

Figure 2.. Estimated Number of Individuals (95% Confidence Interval) Living in the US with Prevalent AD Dementia and Developing Incident AD Dementia in Specific Years between 1994 and 2012

The number of people with prevalent and developing incident AD in millions and the 95% confidence limits for these counts is shown in the two panels. The left panel shows the number of people with prevalent AD dementia. The right panel shows the number of people with incident AD dementia. The estimated numbers are estimated based on the CHAP study sample.