Prevalence of cognitive impairment and dementia as defined by neuropsychological test performance

The Canadian Study of Health and Aging (CSHA) provided a population-based e stimate of the prevalence of dementia of 8% for those aged 65 and older. Ot her studies have produced both higher and lower prevalence estimates. Facto rs that may contribute to these differences include: the use of or the reli ance on neuropsychological testing, the consideration of functional impairm ent as a criterion for dementia and the inclusion of the category of cognit ive impairment without dementia in the diagnostic classification, We examin ed the impact of these methodological factors by reanalyzing the CSHA datab ase for those individuals who completed neuropsychological testing. If the diagnosis of dementia required only impaired neuropsychological test perfor mance, there was an increased prevalence of dementia relative to the clinic al consensus diagnosis, but including the requirement of functional impairm ent for dementia reduced this discrepancy. The findings illustrate the need for clear operationalization of diagnostic criteria for cognitive impairme nt and dementia in neuroepidemiological studies. Copyright (C) 2000 S. Karg er AG, Basel.