The Canadian Journal of Neurological Sciences

18 Although there are many studies on the epidemiology of dementia, there are relatively few longitudinal studies that address progression to dementia in individuals whose cognition was well characterized at baseline. Identifying those at higher risk for the development of dementia is an important goal. Studies indicate that up to 12% of normal older adults became cognitively impaired over two years1 and that up to 80% of individuals initially identified as cognitively impaired eventually progress to dementia.2-5 While a number of variables have been associated with the development of dementia,6-9 these factors are often derived from studies of pre-selected groups such as those ABSTRACT: Objectives: We examined whether easily attainable variables were useful in predicting who became demented over a five year period and determined the rates of incident dementia for different categories of mild cognitive impairment. Methods: This was a cohort study of subjects recruited nationally in a population-based survey of Canadians 65 years and older (the Canadian Study of Health and Aging). After standardized clinical assessments, a subset of subjects (n=1782) was categorized as not demented at time one. Identical study methods allowed a reassessment of the cognitive status of surviving subjects (n=892) five years later. Results: Three baseline variables (Modified Mini Mental State (3MS) score, subject’s age, and an informant’s report of the presence of memory problems) were statistically significant predictors of the development of a dementia. An equation incorporating these three variables had a sensitivity of 79% and a specificity of 56% for predicting dementia among survivors at time two. An equation substituting the MMSE for the 3MS showed similar results. The various categories of mild cognitive impairment examined showed significantly different likelihoods for the subsequent development of a dementia. Some categories with a higher dementia risk were characterized by inclusion criteria requiring neuropsychological test scores that were greater than one standard deviation (SD) below the mean of age based normative data. Conclusion: In the absence of extensive laboratory, radiologic or neuropsychological tests, simple variables that can be easily determined in the course of a single clinical encounter were useful in predicting subjects with a higher risk of developing dementia. Attempts to use neuropsychological results to predict the development of dementia should look for significant impairments on age-standardized tests.