The presence of cognitive impairment corresponds with declines in adaptive functioning (Cahn-Weiner, Ready, & Malloy, 2003). Although memory loss is often highlighted as a key deficit in neurodegenerative diseases (Arvanitakis et al., 2018), research indicates that processing speed may be equally important when predicting functional outcomes in atypical cognitive decline (Roye et al., 2022). Additionally, the development of performance-based measures of adaptive functioning offers a quantifiable depiction of functional deficits within a clinical setting. This study investigated the degree to which processing speed explains the relationship between immediate/delayed memory and adaptive functioning in patients diagnosed with mild and major neurocognitive disorders using an objective measure of adaptive functioning.

Participants (N = 115) were selected from a clinical database of neuropsychological evaluations. Included participants were ages 65+ (M = 74.7, SD = 5.15), completed all relevant study measures, and were diagnosed with Mild Neurocognitive Disorder (NCD; N = 69) or Major NCD (N = 46). They were majority white (87.8%) women (53.0%). The Texas Functional Living Scale was used as a performance-based measure of adaptive functioning. The Coding subtest from the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS-CD) was used to measure information processing speed. Composite memory measures for Immediate Recall and Delayed Recall were created from subtests of the RBANS (List Learning, Story Memory, and Figure Recall) and the Wechsler Memory Scale-IV (Logical Memory and Visual Reproduction). Multiple regressions were conducted to evaluate the importance of memory and information processing speed in understanding adaptive functioning. Age and years of education were added as covariates in regression analyses.

Significant correlations (p < .001) were found between adaptive functioning and processing speed (PS; r = .52), immediate memory (IM; r = .43), and delayed memory (DM; r = .32). In a regression model with IM and DM predicting daily functioning, only IM significantly explained daily functioning (rsp = .24, p = .009). A multiple regression revealed daily functioning was significantly and uniquely associated with IM (rsp = .28, p < .001) and PS (rsp = .41, p < .001). This was qualified by a significant interaction effect (rsp = -.29, p = .001), revealing that IM was only associated with adaptive functioning at PS scores lower than the RBANS normative 20th percentile.

Results suggest that processing speed may be a more sensitive predictor of functional decline than memory among older adults with cognitive disorders. These findings support further investigation into the clinical utility of processing speed tests for predicting functional decline in older adults.