Clinical Manifestations

Area of Science:

• Neuroscience
• Gerontology
• Cognitive Psychology

Background:

• Repeated cognitive testing can lead to practice effects (PEs), influencing performance over time.
• Adjusting for PEs is important for accurate detection of mild cognitive impairment (MCI) and validity of Alzheimer's biomarker concordance.
• The persistence of PEs across multiple long-term follow-ups, alongside age-related decline, requires further investigation.

Purpose of the Study:

• To examine the persistence of practice effects (PEs) across 17 years in a nonclinical sample from midlife to old age.
• To assess the impact of PE adjustment on cognitive scores and mild cognitive impairment (MCI) prevalence over time.
• To determine the extent to which PEs influence longitudinal cognitive assessments in aging.

Main Methods:

• Utilized data from the Vietnam Era Twin Study of Aging (VETSA) with 1,608 male participants across 4 waves (ages 56-73).
• Estimated PEs for 30 tests using generalized estimating equations, comparing returnees to attrition replacements at each wave.
• Calculated unadjusted and PE-adjusted cognitive scores for multiple domains and compared MCI prevalence before and after PE adjustment.

Main Results:

• Significant PEs were observed for numerous cognitive tests across all follow-up waves, particularly in episodic and visual memory.
• PE-adjusted cognitive scores were consistently lower than unadjusted scores, except for fluency.
• MCI prevalence increased by up to 20% after PE adjustment, indicating earlier detection.

Conclusions:

• Practice effects (PEs) are persistent across multiple decades and long testing intervals.
• Even minor PEs can significantly impact cognitive scores, leading to earlier identification of mild cognitive impairment (MCI).
• Accounting for PEs in longitudinal studies is essential for accurate diagnosis, improved clinical trial efficiency, and reduced costs.