Beyond retest gains: episodic memory practice effects and longitudinal cognitive trajectories in cognitively healthy...

Practice effects in repeated neuropsychological assessment are usually treated as measurement bias, although they may carry meaningful information. It remains unclear whether individual differences in episodic memory practice effects are associated with cognitive level and longitudinal change beyond generic retest-related gains.

We analyzed data from 442 cognitively healthy middle-aged and older adults who completed neuropsychological assessments in 2018, 2021, and 2025. Retest-related offsets were modeled explicitly to separate sample-level retest gains from continuous longitudinal change. A baseline-adjusted episodic memory practice effect was derived from change in episodic memory between baseline and first follow-up and included in linear mixed-effects models of global cognition and specific domains, adjusting for age, biological sex, and education.

Retest-related gains were significant at both follow-up waves. After accounting for these offsets, greater episodic memory practice effect was associated with higher global cognitive performance and more favorable longitudinal change. In a robustness analysis using a non-memory global composite, the association with cognitive level remained significant, whereas the association with longitudinal change was attenuated. Domain-specific analyses showed strongest associations for episodic memory, followed by processing speed; reasoning was associated with cognitive level but not change, with no significant associations for attention/working memory or cognitive flexibility.

Episodic memory practice effects appear to carry meaningful information beyond generic retest-related gains. Explicitly modeling retest effects while preserving interindividual differences in practice-related improvement may refine the characterization of longitudinal cognitive trajectories and help identify subtle early differences in cognitive resilience and vulnerability.