A – 118 Exploring A Novel Executive Function Metric in Alzheimer’s Dementia: A Secondary Analysis of a HD-tDCS Clinical Trial

Abstract Objective High-definition transcranial direct current stimulation (HD-tDCS) over the prefrontal cortex showed improvement on some executive function (EF) measures in a pilot trial for mild-to-moderate Alzheimer’s dementia (AD). However, many could not finish an EF measure, the DKEFS Color Word Interference (CWI), within the administration time due to impairment, preventing an analysis of typical scores. This secondary analysis developed a novel performance metric to evaluate DFEFS-CWI outcomes within the trial. Method Participants were randomized to 10 sessions of HD-tDCS at 0 mA, 1 mA or 2 mA current intensities, and the DKEFS-CWI was administered pre- and immediately post-intervention. Of the total trial sample (n=23), only 14 participants from the 0 mA (n=3), 1 mA (n=6), and 2 mA (n=5) conditions understood the task and attempted the Inhibition trial. An item efficiency index score, calculated as the number of correct plus self-corrected items divided by the total administration time, was examined for these participants. Analyses of covariance compared the index score for the active groups (1 mA and 2 mA separately) to 0 mA sham group while controlling for baseline performance. Results No statistically significant differences between sham and either 1 mA (p=.82, d=.19) or 2 mA (p=.94, d=.07) HD-tDCS groups were found post-intervention. Conclusion This HD-tDCS paradigm was not associated with a change in the DKEFS-CWI Inhibition efficiency index score. Conclusions could be limited by a substantial portion of the sample being incapable of attempting the DKEFS-CWI. Future research needs to establish which EF measures are suitable clinical trial metrics for impaired patients with AD.