Pragmatic approaches to handling practice effects in longitudinal cognitive aging research

INTRODUCTIONThe challenge of accounting for practice effects (PEs) when modeling cognitive change was amplified by the COVID-19 pandemic, which introduced period and mode effects that may bias the estimation of cognitive trajectory. METHODSIn three Kaiser Permanente Northern California prospective cohorts, we compared predicted cognitive trajectories and the association of grip strength with cognitive decline using three approaches: (1) no acknowledgment of PE, (2) inclusion of a wave indicator, and (3) constraining PE based on a preliminary model (APM) fit using a subset of the data. RESULTSAPM-based correction for PEs based on balanced, pre-pandemic data, and with current age as the timescale produced the smallest discrepancy between within-person and between-person estimated age effects. Estimated associations between grip strength and cognitive decline were not sensitive to the approach used. DISCUSSIONConstraining PEs based on a preliminary model is a flexible, pragmatic approach allowing for meaningful interpretation of cognitive change. HighlightsThe magnitude of practice effects (PEs) varied widely by study.When PEs were present, the three PE approaches resulted in divergent estimated age-related cognitive trajectories.Estimated age-related cognitive trajectories were sometimes implausible in models that did not account for PEs.The associations between grip strength and cognitive decline did not differ by the PE approach used.Constraining PEs based on estimates from a preliminary model allows for a meaningful interpretation of cognitive change.

Automated summary

The challenge of accounting for practice effects (PEs) in modeling cognitive change was amplified by the COVID-19 pandemic. Comparing three approaches, we found that correcting for PEs based on a preliminary model produced more accurate estimations of cognitive trajectories, and the association between grip strength and cognitive decline was not sensitive to the approach used.