Performance on face-valid IADL tasks in the lab is less related to independent performance of similar tasks at home than is performance on the D-KEFS: a face validity paradox.

OBJECTIVE: Estimating functional independence is a critical component of neuropsychological evaluations in older adults. Commonly, three methods are used to estimate a patient's ability to engage in instrumental activities of daily living (IADLs): (1) rating scales of functional independence and (2) performance-based measures comprising IADL tasks (reflecting two face-valid approaches), and (3) performance-based measures of executive functions (EF; reflecting a more theory-based approach). The purpose of the present study was to compare these three methods' abilities to predict independent IADL capacity at home. METHOD: Community-dwelling older adults (n = 114) completed self-report and performance-based measures of IADLs, as well as traditional tests of EF at baseline. Following, participants completed the DAILIES protocol comprising 3 weeks of IADL tasks (e.g., paying bills, rescheduling appointments, etc.) performed independently at home. RESULTS: Analyses showed that (a) EF performance speed and self-reported IADLs emerged as unique predictors (i.e., beyond each other) of the accuracy of the DAILIES task completion, and (b) EF performance speed also accounted for variance in the timeliness of DAILIES task completion. These relationships held beyond general cognitive status. However, receiver operating characteristic (ROC) analyses revealed that only EF performance speed had utility in identifying participants with below average accuracy and timeliness on the DAILIES protocol. CONCLUSION: These findings suggest that traditionally measured EF may have more incremental utility than at least some more face-valid predictors (i.e., certain performance-based or self-reported IADLs) in predicting independent IADL capacity at home, at least among older adults without a diagnosis of a cognitive disorder.