Adaptive Functioning Among Older Adults: The Essence of Information Processing Speed in Executive Functioning

Objective The current study investigated the degree to which information processing speed mediates the association between executive functioning and adaptive functioning among older adults. Method Cases (N = 239) were selected from a clinical database of neuropsychological evaluations. Inclusion criteria were age 60+ (M = 74.0, standard deviation = 6.9) and completion of relevant study measures. Participants were majority White (93%) women (53.1%). The Texas Functional Living Scale was used as a performance-based measure of adaptive functioning. Information processing speed was measured using the Coding subtest from the Repeatable Battery for the Assessment of Neuropsychological Status. Executive functioning performance was quantified using part B of the Trail Making Test, Controlled Oral Word Association Test, and Similarities and Matrix Reasoning subtests from the Wechsler Abbreviated Scale of Intelligence, second edition. Mediation models were assessed with bootstrapped confidence intervals. Results Information processing speed mediated all measures of executive functioning. Direct effects were significant for all models (ps < 0.03), suggesting that executive functioning maintained unique associations with adaptive functioning. Follow-up analyses indicated no evidence for moderation of the mediation models based on diagnostic group. Additional models with executive functioning mediating information processing speed and adaptive functioning revealed inconsistent mediation, with smaller effects. Conclusions Results highlight the importance of information processing speed in understanding real-world implications of pathological and non-pathological cognitive aging. Information processing speed mediated all relationships between executive functioning and adaptive functioning. Further investigation is warranted into the importance of processing speed in explaining associations of other cognitive domains with adaptive functioning.