Clinical issues relating to the diagnosis of mild dementia in a British community survey

Many epidemiologists base their diagnoses of dementia on scores on brief cognitive tests, but the border between normal aging and mild dementia is so poorly understood that simple demarcations cannot adequately encapsulate the wealth of clinical material that needs to be taken into account in assigning diagnostic labels. Data from a British study of the prevalence and natural history of dementia, in which diagnoses of dementia were made by clinicians using a new, standardized interview schedule, are presented to demonstrate the effects of physical disability, psychiatric illness, and other factors on memory impairment and performance in everyday life. Our purpose is not to insist that clinicians are always correct but rather to highlight the complexities involved and the need for investigators to be more open about the way in which they distinguish between physical, psychiatric, and cognitive infirmities.