Cognitive impairment in the nondemented elderly. Results from the Canadian Study of Health and Aging

E. M. Ebly, D. B. Hogan and I. M. Parhad
Department of Pathology, University of Calgary, Alberta.

STUDY OBJECTIVE: To describe a population that was categorized as "cognitively impaired not demented" (CIND) and to examine the utility of some of the proposed criteria for describing this degree of cognitive impairment. DESIGN: Population-based prevalence study of dementia in those subjects who were 65 years and older. SETTING: Community and institutional settings in Canada. SUBJECTS: Individuals who underwent a clinical evaluation (N = 2914). INTERVENTION: Initial screening with the Modified Mini-Mental State Examination (3MS) to identify potential cognitive impairment; the 3MS was followed by a detailed clinical examination to confirm the presence of dementia and to determine the probable cause. Clinical examinations were performed on all those subjects who were residing in institutions, those in the community with a 3MS score less than 78, and a sample of those in the community with a 3MS score of 78 or more. Neuropsychological testing was performed as part of the clinical examination when the 3MS score was 50 or more. At the conclusion of the assessment, subjects were categorized as being cognitively normal, CIND, and demented. MEASUREMENTS: Frequency of a diagnosis of CIND; demographical, cognitive, and functional characteristics of cognitively normal and CIND subjects and those with early and late dementia; and proportion of subjects who were CIND and met the proposed criteria. RESULTS: Subjects who were categorized as CIND were common and fell between cognitively normal subjects and those with dementia in terms of age, 3MS score, general intellectual function, and performance of daily activities. Because of the restrictive inclusion and exclusion criteria, the proposed criteria for cognitive impairment described only 30% of our subjects who were CIND. CONCLUSIONS: Subjects who were categorized as CIND appeared to be distinct from and intermediate between subjects with dementia and cognitively normal subjects. Most individuals did not meet the criteria that were evaluated for describing this group. While the various criteria that were evaluated may accurately define a select subset of cognitively impaired individuals, the natural history and prognosis of such groups, currently unknown, may not be generalizable to the larger population of subjects who are CIND. Further work is needed to clearly define this group, and longitudinal studies are required to determine an outcome.