Cognitive Trajectory Changes Over 20 Years Before Dementia Diagnosis: A Large Cohort Study

Area of Science:

• Neuroscience
• Gerontology
• Cognitive Psychology

Background:

• Longitudinal studies indicate cognitive decline precedes dementia diagnosis by many years.
• Understanding the early trajectory of cognitive changes is crucial for timely intervention.

Purpose of the Study:

• To estimate changes in cognitive function trajectory relative to normal aging.
• To identify the timing of cognitive decline and acceleration before clinical dementia diagnosis.
• To assess the influence of sex, education, and APOE genotype on cognitive trajectories.

Main Methods:

• Prospective cohort study of 4,315 community-dwelling individuals aged 65+ without baseline dementia.
• Utilized Cognitive Abilities Screening Instrument (CASI) item response theory (IRT) scores to model longitudinal cognitive trajectories.
• Assessed the impact of sex, education level, and APOE genotype on cognitive decline patterns.

Main Results:

• Significant cognitive decline was detected at least 10 years before clinical dementia diagnosis.
• A change point in cognitive decline trajectory was estimated at 3.1 years pre-diagnosis, followed by accelerated decline.
• Male gender, lower education, and APOE ε4 alleles were associated with lower average CASI IRT scores.

Conclusions:

• Global cognitive function decline is detectable a decade before dementia diagnosis.
• Cognitive decline accelerates approximately 3 years prior to clinical diagnosis.
• Early detection of cognitive changes may enable earlier intervention strategies.