Effectiveness of Transcranial Stimulation on Cognitive Abilities of Older Adults with Mild Cognitive Impairment

Background/Objectives: Aging leads to cognitive decline that may progress to dementia. Transcranial direct current stimulation (tDCS) has emerged as a strategy to improve cognitive functions in older adults with mild cognitive impairment (MCI). This study reviews the effectiveness of tDCS in these populations. Methods: A systematic review and meta-analysis was conducted following the PRISMA 2020 guidelines. Randomized controlled trials obtained from PubMed, Scopus, Cinahl, and Web of Science were included. Studies with tDCS intervention in older adults with MCI were selected, excluding those without a control group or that did not measure relevant cognitive variables. Methodological quality was analyzed with the PEDro scale and a meta-analysis was applied with random-effects models. Results: A total of 27 studies were included in this review, of which 13 were part of the meta-analysis. tDCS showed significant improvements in global cognitive function (p < 0.001) and selective attention (p = 0.044), but not in mental flexibility or visual attention. Positive effects on quality of life and depressive symptoms were also reported in some studies. Conclusions: tDCS may improve cognitive functions in older adults with MCI, but inconsistencies persist in its magnitude and duration. It is recommended to standardize protocols and conduct studies with greater methodological rigor and long-term follow-up.