Prospective memory impairment as an early indicator of dementia.

Theoretical accounts of the cognitive processes involved in prospective memory imply that performance on such tasks will be more vulnerable than retrospective memory tests to the early stages of dementia. This hypothesis is examined in elderly subjects from a general population sample which includes demented subjects. We report the findings on three tests of prospective memory from the Rivermead Behavioural Memory Test (Wilson et al., 1985) and compare it with measures of retrospective memory for recently acquired information. In contrast to retrospective memory where subjects with minimal dementia perform at a level intermediate between normals and more demented subjects, the subjects with minimal dementia perform as poorly as more demented subjects on the prospective memory tests. These findings provide evidence that prospective memory tasks are particularly sensitive to the early stages of dementia. Covariance analysis and the pattern of intercorrelations found between prospective and retrospective memory lead to alternative hypotheses about the cognitive processes involved in prospective memory and the way in which they break down.