Brain Structures and Cognitive Decline: Moderation Analysis of the PACt-MD Randomized Clinical Trial of Brain Stimulation Plus Cognitive Remediation in Older Adults With Remitted Depression or Mild Cognitive Impairment

OBJECTIVE: To identify which patients with remitted major depressive disorder (rMDD) or mild cognitive impairment (MCI) benefit from cognitive remediation (CR) plus transcranial direct current stimulation (tDCS). DESIGN: We conducted a moderator analysis to examine the effects of baseline brain magnetic resonance imaging (MRI) measures on the impact of CR + tDCS on cognitive decline in Prevention of Alzheimer's dementia with CR plus tDCS in MCI and Depression (PACt-MD), a double-masked randomized two-arm controlled trial with assessments at baseline, two months, and yearly for three to seven years. SETTING: Five academic hospitals in Toronto, Canada. PARTICIPANTS: A total of 246 participants with rMDD, MCI, or both, with an analyzable baseline MRI. INTERVENTION: CR + tDCS or sham CR + sham tDCS. MEASUREMENTS: Overall cortical thickness, overall fractional anisotropy, and cortical thickness in an a-priori composite region of interest (ROI); changes in global cognition, executive function, or verbal memory. RESULTS: Overall cortical thickness moderated decline in global cognition (Χ² = 10.43, df = 3, p = 0.015); ROI cortical thickness moderated treatment-related changes in global cognition (Χ² = 29.05, df = 3, p