The ups and downs matter: Magnitudes of fluctuations in executive functions predict daily functioning in older adults

Objective: Intra-individual variability in executive functions (EF), assessed both behaviorally and via self-report, may serve as a predictor of instrumental activities of daily living (IADLs), whereas mean self-reported EF levels typically do not. No prior research has simultaneously examined associations among (a) day-to-day mean levels and fluctuations of EF self-report, (b) day-to-day mean levels and fluctuations of EF performance, and (c) performance of IADL tasks at home. This study examined the extent to which EF performance and EF self-report (both mean levels and daily fluctuations) relate to each other and to at-home IADL performance. Method: One-hundred and twenty-seven community dwelling older adults responded to daily questions about their EF abilities and completed daily EF and IADL tasks, all independently at home across 18 days. Results: IADL performance was predicted by overall mean EF performance and by the magnitude of fluctuations in both EF performance and EF self-report, with all three variables contributing uniquely to the model and together accounting for 27% of IADL variance (reflecting a large effect size), although fluctuations in self-report did not survive covariate analyses. Mean levels of self-reported EF did not correlate with performance on EF or IADL tasks. Conclusion: Both mean levels and fluctuations in EF performance across days uniquely contributed to the prediction of daily functioning, demonstrating incremental validity of each variable. Self-report of EF (both fluctuations and mean levels) did not incrementally improve prediction beyond covariates.