A two-year longitudinal study of cognitive function in normal aging and Alzheimer's disease.

A group of 136 elderly subjects were administered a comprehensive neuropsychological test battery, which was readministered 2 years later. Among the 136 elderly subjects, 86 were assigned a diagnosis of probable Alzheimer's disease. An additional 33 young subjects were administered the assessment battery at baseline only. The normal elderly group exhibited no decline in cognitive test performance over the 2-year follow-up interval. Subjects with mild cognitive impairment, however, were as likely to deteriorate between baseline and follow-up as the more severely impaired subjects. The tests that exhibited longitudinal decline in the Alzheimer's disease patients constituted a subset of the tests that revealed cross-sectional deficits relative to the normal elderly. Differences in baseline cognitive test performance and in rate of cognitive deterioration were examined in relatively young versus relatively old Alzheimer's disease patients. Potential psychometric predictors of cognitive decline in the normal elderly were identified.