The validity of cognitive testing in screening for dementia.

The concept of "cognitive impairment," as an indicator of dementia, defined in 1980 as a loss of intellectual abilities of sufficient severity to interfere with social or occupational functioning, is the model which has been adopted for a condition, which has recently been reclassified from an "organic" to a "cognitive disorder." Data derived from the assessment of a sample of older people demonstrated the extreme sensitivity of a widely employed cognitive assessment instrument to all levels of educational experience, and educational correlates, notably level of physical disability, were identified as other independent predictors of test performance. The analyses raise questions with regard to the reinterpretation of "lack of education," from a confounding factor in prevalence estimates of cognitive impairment to a "risk factor" for dementia, and support those who have questioned the validity of the one-dimensional "cognitive paradigm," and the trend to diagnosis based upon objective assessment with standardized instruments.