Mild Cognitive Impairment and Dementia Prevalence: The Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS).

INTRODUCTION: We examined prevalence of mild cognitive impairment (MCI) and dementia in the Atherosclerosis Risk in Communities (ARIC) Neurocognitive Study.

METHODS: Beginning in June, 2011, we invited all surviving ARIC participants to undergo cognitive, neurological and brain imaging assessments to diagnose MCI or dementia and assign an etiology for the cognitive disorder.

RESULTS: Of 10713 surviving ARIC participants (age range 69-88 yrs), we ascertained cognitive diagnoses in 6471 in-person, 1966 by telephone interviews (participant or informant) and the remainder by medical record review. The prevalence of dementia was 9.0% and MCI 21%. Alzheimer's disease was the primary or secondary etiology in 76% of dementia and 75% of MCI participants. Cerebrovascular disease was the primary or secondary etiology in 46% of dementia and 32% of MCI participants.

DISCUSSION: MCI and dementia were common among survivors from the original ARIC cohort. Nearly 30% of the ARIC cohort received diagnoses of either dementia or MCI, and for the majority of these individuals (about 75%) the etiologic basis was attributed to Alzheimer's disease.