Patterns of cognitive decline in presymptomatic Alzheimer disease - A prospective community study

Background: Specific patterns of decline over time were evaluated across a spectrum of cognitive measures in presymptomatic Alzheimer disease (AD) wit hin a community sample. Methods: A total of 551 individuals completed a battery of standard cogniti ve tests 3.5 and 1.5 years before outcome (clinical onset of AD vs continue d nondemented status) within a prospective community-based study of AD. Tes t score changes in 68 cases (who subsequently developed symptomatic AD) and 483 controls (who remained nondemented) on each of 15 cognitive measures w ere transformed into z scores adjusted for age, sex, and education. A case- control rate ratio of the proportions of individuals who showed "cognitive decline" on each test was calculated, representing the relative magnitude o f cognitive decline on each test in presymptomatic AD compared with normal aging. Results: Declines in Trail-Making Tests A and B and Word List delayed recog nition of originals and third immediate learning trial had the highest rate ratios, larger than 3.0 (P < .01). These were followed by Word List delaye d recognition of foils and delayed recall, Consortium to Establish a Regist ry for Alzheimer's Disease Praxis, Clock Drawing, the Boston Naming Test, a nd Orientation, with rate ratios between 1.7 and 3.0 (P < .05). Conclusions: Memory and executive dysfunction showed the greatest decline o ver time in individuals who would clinically manifest AD 1.5 years later. T hese findings might help us understand the underlying evolution of the earl y neurodegenerative process. They highlight the importance of executive dys function early in the disease process and might facilitate early detection of AD.