Combined home-delivered transcranial direct current stimulation and cognitive training in older adults with mild cognitive impairment due to Alzheimer's disease: a randomized, single-blind, sham-controlled trial

Background Non-pharmacological interventions such as transcranial direct current stimulation (tDCS) and cognitive training (CT) may benefit cognition in older adults with mild cognitive impairment due to Alzheimer's disease (MCI-AD), yet evidence on combined, home-delivered protocols remains limited. This study evaluated the effectiveness of a combined home-delivered combined tDCS and CT intervention across multiple cognitive domains in individuals with MCI-AD. Methods We conducted a randomized, single-blind, sham-controlled trial in 41 participants (≥ 65 years) with MCI-AD, allocated to four experimental conditions: (1) tDCS combined with CT, (2) tDCS without CT, (3) sham tDCS combined with CT, and (4) sham tDCS without CT. Interventions were delivered at participants' homes by trained staff across 10 daily sessions. Outcomes (MMSE; TAVEC Trial 1/Total/Delayed; Forward Digit Span) were assessed at baseline, post-intervention, and 1-month follow-up. Data were analyzed with 4 × 3 mixed-design ANOVAs (group×time) with Bonferroni-adjusted post hoc tests; partial eta-squared was reported as effect size. Results Significant group × time interactions were found for global cognition (MMSE), immediate memory (TAVEC Trial 1), verbal learning (TAVEC Total), and short-term memory (Forward Digit Span) (all p<.05). The combined tDCS + CT group showed sustained improvements across the significant cognitive domains at post-intervention and follow-up. Conclusions This randomized controlled trial provides evidence that a home-delivered combined intervention of tDCS and CT can enhance cognitive performance in older adults with MCI-AD. Improvements were domain-specific and sustained over short follow-up. While the modest sample and limited follow-up warrant cautious interpretation