Linking behavioral variability to daily function in stroke survivors: the mediating role of cognitive and motor mechanisms

Stroke significantly impacts an individual’s ability to perform instrumental activities of daily living (IADLs). Intraindividual variability (IIV) is characterized by heightened fluctuations across multiple attempts at a task. IIV is a behavioral indicator of central nervous system instability that may contribute directly to compromised capacity to perform IADLs following stroke. This study aimed to investigate the relationship between IIV and IADL performance in stroke survivors and determine whether executive control and/or motor capacity serve as mediating pathways. In this cross-sectional observational study, 84 stroke survivors and 35 healthy older adults participated. We derived latent factor scores for IIV from reaction time and goal directed tasks, IADL performance from the Observed Task of Daily Living and Functional Activities Questionnaire, executive control from tests of divided attention, selective attention, cognitive flexibility, and processing speed, and motor capacity from grip and ankle strength. We examined the association between IIV and IADL performance and conducted a parallel mediation analysis to determine whether executive control and motor capacity mediated this relationship. Higher IIV was associated with compromised IADL performance. Mediation analyses showed that the relationship between IIV and IADL performance was significantly mediated by executive control but not motor capacity while controlling for the covariate of age. Behavioral variability after stroke impacts everyday function primarily through a cognitive pathway. These findings highlight executive control as a key therapeutic target in stroke rehabilitation to mitigate the functional consequences of neural instability on instrumental activities of daily living.