Cognitive decline in an elderly population--a two wave study of change.

A sample of 1111 survivors from a population aged 75 years and over completed the Mini-Mental State Examination (MMSE) twice, separated by 28 months on average. There was a mean decline of 1.3 points in MMSE score. With increasing age, mean drop in score also increased. The proportion at each age identified as newly cognitively impaired according to any standard cut-point on MMSE rose markedly. Mean decline was greater in women than men even after adjustment for age. Cognitive change on the MMSE was approximately unimodally and normally distributed. This distribution was a marked contrast to the distribution of MMSE scores themselves, which was skewed due to truncation of scores at the maximum. The decline was not due to the inclusion of individuals with physical impairment. These findings indicate that cognitive decline, like dementia, becomes increasingly common with advancing age, and suggest that dementia may be regarded as one extreme of the continuum of cognitive decline.