Evaluation of dementia in the cardiovascular health cognition study.

To describe a methodology to evaluate dementia and frequency of different types of dementia and prevalence of the Cardiovascular Health Study (CHS). The CHS is a longitudinal study of cardiovascular disease among community-dwelling individuals over the age of 65. Of the 5,888 participants in the original study, 3,608 had a magnetic resonance imaging (MRI) of the brain in 1991, and formed the cohort for the dementia study. The CHS included yearly measures of cognitive function and, from 1998 to 2000, participants were evaluated for dementia by detailed neurological, and neuropsychological examinations. The possible cases of dementia and mild cognitive impairment (MCI) were adjudicated by a review committee of neurologists and psychiatrists. There were 480 cases of (13.3%) incident dementia in the total sample, 227 (6.3%) prevalent dementia, 577 (16.0%) MCI, and 2,318 (64.4%) normal. The adjudication committee classified 69% of the incident dementia as Alzheimer's disease (AD), 11% as vascular dementia (VaD), 16% as both, and 4% as other types. There was a substantial agreement between pre- and postMRI diagnosis of types of dementia. The frequency of dementia within the CHS cohort which survived to the end of the study in 1998-1999, was 13.5% for white men, 14.5% for white women, 22.2% for black men and 23.4% for black women. The CHS has developed a methodology for longitudinal studies of dementia in large cohorts and represents the largest study of dementia including cognitive testing, MRI and genetic markers.