Is non-invasive brain stimulation effective for cognitive enhancement in Alzheimer?s disease? An updated meta-analysis

Objective: Alzheimer's disease dementia (AD) and its preclinical stage, mild cognitive impairment (MCI), are critical issues confronting the aging society. Non-invasive brain stimulation (NIBS) techniques have the potential to be effective tools for enhancing cognitive functioning. The main objective of our meta -analysis was to quantify and update the status of the efficacy of repetitive Transcranial Magnetic Stimulation (rTMS) and Transcranial Direct Current Stimulation (tDCS) when applied in AD and MCI.Methods: The systematic literature search was conducted in PubMed and Web of Science according to PRISMA statement.Results: Pooled effect sizes (Hedges' g) from 32 studies were analyzed using random effect models. We found both, rTMS and tDCS to have significant immediate cognition-enhancing effect in AD with rTMS inducing also beneficial long-term effects. We found no evidence for synergistic effect of cognitive train-ing with NIBS.Conclusions: In AD a clinical recommendation can be made for NEURO-ADTM system and for high -frequency rTMS over the left dorsolateral prefrontal cortex (DLPFC) as probably effective protocols (B -level of evidence) and for anodal tDCS over the left DLPFC as a possibly effective.Significance: According to scientific literature, NIBS may be an effective method for improving cognition in AD and possibly in MCI.(c) 2022 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).