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Improvements in Cogstate Test Performance Depend on Number and Frequency of Prior Tests: Evidence from a Randomized
Audrey R Murchland1,2, Ruijia Chen2, Deborah Blacker1,3,4
1Department of Epidemiology, Harvard T.H. Chan School of Public Health.
Alzheimer Disease and Associated Disorders
|June 1, 2026
Summary
Practice effects (PEs) in cognitive testing can inflate scores, potentially masking age-related cognitive decline. Randomizing testing frequency in longitudinal studies helps quantify these effects accurately.
Area of Science:
- Cognitive aging research
- Neuropsychological assessment
Background:
- Practice effects (PEs) are improvements in cognitive test performance due to repeated exposure.
- Longitudinal studies of cognitive aging must account for PEs.
- Many cognitive assessments claim robustness to PEs, but evidence is limited.
Purpose of the Study:
- To quantify PEs in the Cogstate Brief Battery using a randomized design.
- To assess the impact of testing repetition and frequency on cognitive performance in a large cohort.
Main Methods:
- Utilized data from 14,802 participants in the Nurses' Health Study II.
- Employed conditionally randomized 6- or 12-month testing regimens between 2014 and 2019.
- Examined practice effects from increased testing repetition and frequency.
Main Results:
- Increased testing frequency (twice vs. once previously) at 12 months was linked to higher global cognitive scores (0.13 SD), equivalent to 4.3-6.8 years of aging.
- More frequent testing (6 vs. 12 months) also showed higher scores (0.04 SD), equivalent to 1.3-1.6 years of aging.
- PEs appeared larger in older participants, though formal tests of modification were uncertain.
Conclusions:
- Repetition PEs with Cogstate may obscure age-related cognitive decline over short periods.
- Randomizing testing features is a valuable method for strengthening cognitive aging research.
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