Journal
JOURNAL OF THE AMERICAN GERIATRICS SOCIETY
Volume 65, Issue 12, Pages 2627-2633Publisher
WILEY
DOI: 10.1111/jgs.15077
Keywords
dementia; cognitive function; trajectory changes; change point
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Funding
- National Institute on Aging and U.S. Department of Veterans Affairs [AG033693, AG006781, AG05136]
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BACKGROUND/OBJECTIVES: Longitudinal studies have shown an increase in cognitive decline many years before clinical diagnosis of dementia. We sought to estimate changes, relative to normal aging, in the trajectory of scores on a global cognitive function test-the Cognitive Abilities Screening Instrument (CASI). DESIGN: A prospective cohort study. SETTING: Community-dwelling members of a U. S. health maintenance organization. PARTICIPANTS: Individuals aged 65 and older who had no dementia diagnosis at baseline and had at least two visits with valid CASI test score (N = 4,315). MEASUREMENTS: Average longitudinal trajectories, including changes in trajectory before clinical diagnosis in those who would be diagnosed with dementia, were estimated for CASI item response theory (IRT) scores. The impact of sex, education level, and APOE genotype on cognitive trajectories was assessed. RESULTS: Increased cognitive decline relative to normal aging was evident in CASI IRT at least 10 years before clinical diagnosis. Male gender, lower education, and presence of >= 1 APOE epsilon 4 alleles were associated with lower average IRT scores. In those who would be diagnosed with dementia, a trajectory change point was estimated at an average of 3.1 years (95% confidence interval 3.0-3.2) before clinical diagnosis, after which cognitive decline appeared to accelerate. The change point did not differ by sex, education level, or APOE epsilon 4 genotype. There were subtle differences in trajectory slopes by sex and APOE epsilon 4 genotype, but not by education. CONCLUSION: Decline in average global cognitive function was evident at least 10 years before clinical diagnosis of dementia. The decline accelerated about 3 years before clinical diagnosis.
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