Incidence of dementia and cognitive decline in over-75s in Cambridge: overview of cohort study.

This paper summarises the methods and some of the findings of a large cohort study of dementia and cognitive decline in subjects aged over 75 years in Cambridge, particularly regarding the incidence wave. From a sample of 1968 subjects previously studied in a prevalence study in 1985-1987, survivors were restudied at 2.4 years, in a two-stage design employing the Mini; Mental State Examination (MMSE) and the Cambridge Examination for Mental Disorders of the Elderly (CAMDEX). High incidence rates of dementia were found, which rose steeply with age, particularly for Alzheimer's disease. New minimal dementia and milder cognitive impairment were also common. Cognitive decline on the MMSE showed a near normal, non-bimodal distribution. The sample has since been restudied at intervals for a total of up to 9 years to document longitudinal cognitive change. Brains have been obtained for post mortem neuropathological and molecular biological study, particularly of the early sequential changes associated with cognitive decline and dementia.