Assessment of medication management, an instrumental activity of daily living (IADL), is particularly important among Veterans, who are prescribed an average of 2540 prescriptions per year (Nguyen et al., 2017). The Pillbox Test (PT) is a brief, performance-based measure that was designed as an ecologically valid measure of executive functioning (EF; Zartman, Hilsabeck, Guarnaccia, & Houtz, 2013), the cognitive domain most predictive of successful medication schedule management (Suchy, Ziemnik, Niermeyer, & Brothers, 2020). However, a validation study by Logue, Marceaux, Balldin, and Hilsabeck (2015) found that EF predicted performance on the PT more so than processing speed (PS), but not the language, attention, visuospatial, and memory domains combined. Thus, this project sought to increase generalizability of the latter study by replicating and extending their investigation utilizing a larger set of neuropsychological tests.

Participants included 176 patients in a mixed clinical sample (5.1% female, 43.2% Black/African American, 55.7% white, Mage = 70.7 years, SDage = 9.3, Medu = 12.6 years, SDedu = 2.6) who completed a comprehensive neuropsychological evaluation in a VA medical center. All participants completed the PT where they had five minutes to organize five pill bottles using a seven-day pillbox according to standardized instructions on the labels. Participants also completed some combination of 26 neuropsychological tests (i.e., participants did not complete every test as evaluations were tailored to disparate referral questions). Correlations between completed tests and number of pillbox errors were evaluated. These tests were then combined into the following six domains: language, visuospatial, working memory (WM), psychomotor/PS, memory, and EF. Hierarchical multiple regression was completed using these domains to predict pillbox errors.

Spearman’s correlation coefficients indicated that 25 tests had a weak to moderate relationship with PT total errors (rs = 0.23 -0.51); forward digit span was not significantly related (rs = 0.13). A forced-entry multiple regression was run to predict PT total errors from the six domains. The model accounted for 29% of the variance in PT performance, F(6, 169) = 11.56, p < .001. Of the domains, psychomotor/PS made the greatest contribution, f(169) = 2.73, p = .007, followed by language, f(169) = 2.41, p = .017, and WM, f(169) = 2.15, p = .033. Visuospatial performance and EF did not make significant contributions (ps>.05). Next, two hierarchical multiple regressions were run. Results indicated that EF predicted performance on the PT beyond measures of PS, AR2 = .02, p = .044, but not beyond the combination of all cognitive domains, AR2 = .00, p = .863.

Results of this study partially replicated the findings of Logue et al. (2015). Namely, EF predicted PT performance beyond PS, but not other cognitive domains. However, when all predictors were entered into the same model, visuospatial performance did not significantly contribute to the prediction of pillbox errors. These results suggest that providers may benefit from investigating medication management abilities when deficits in PS, WM, and/or language are identified. Further research is needed to better understand which domains best predict PT failure.