BACKGROUND: Specific patterns of decline over
time were evaluated across a spectrum of cognitive
measures in presymptomatic Alzheimer disease (AD)
within a community sample.
METHODS: A total
of 551 individuals completed a battery of standard
cognitive tests 3.5 and 1.5 years before outcome
(clinical onset of AD vs continued nondemented
status) within a prospective community-based study
of AD. Test score changes in 68 cases (who
subsequently developed symptomatic AD) and 483
controls (who remained nondemented) on each of 15
cognitive measures were 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 of
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
recognition of originals and third immediate
learning trial had the highest rate ratios, larger
than 3.0 (P<.01). These were followed by Word List
delayed recognition of foils and delayed recall,
Consortium to Establish a Registry for Alzheimer's
Disease Praxis, Clock Drawing, the Boston Naming
Test, and Orientation, with rate ratios between 1.7
and 3.0 (P<.05).
CONCLUSIONS: Memory and
executive dysfunction showed the greatest decline
over time in individuals who would clinically
manifest AD 1.5 years later. These findings might
help us understand the underlying evolution of the
early neurodegenerative process. They highlight the
importance of executive dysfunction early in the
disease process and might facilitate early detection
of AD.