COGNITIVE MARKERS PRECEDING ALZHEIMERS DEMENTIA IN THE HEALTHY OLDEST-OLD

OBJECTIVE: To look for preclinical markers of Alzheimer's dementia in a sample of healthy, oldest old individuals. DESIGN: Prospective, long itudinal study of individuals examined at yearly intervals with neurop sychological tests selected to be sensitive to the early detection of dementia. PARTICIPANTS: One hundred and thirty-nine community-dwelling , functionally independent, healthy individuals 65 to 106 years of age who met strict criteria for lack of dementia at entry. Incident demen tia cases consisted of 16 volunteers all 80 years old or older who dev eloped dementia of the Alzheimer's type and 31 volunteers 80 years old and older showing no evidence of dementia during a mean 2.8-year foll ow-up interval. MEASUREMENTS: Scores on 10 neuropsychological measures were analyzed for the initial examination when none of the volunteers showed clinical evidence of dementia and for the two subsequent yearl y examinations. RESULTS: Individuals who subsequently developed dement ia showed evidence of verbal memory impairment at their initial examin ation, which was a mean of 2.8 years before clinical evidence of demen tia. The average yearly incidence rate for dementia in those 80 years of age and older was 12%. Performance of individuals who did not devel opment dementia remained relatively stable during follow-up for up to 5 years. CONCLUSION: Alzheimer's disease has a preclinical stage in wh ich verbal memory decline is the earliest sign. Dementia in the oldest old is distinguishable from age-related cognitive decline.