Effects of Noninvasive Brain Stimulation (NIBS) on Cognitive Impairment in Mild Cognitive Impairment and Alzheimer Disease

Abstract

Supplemental Digital Content is available in the text. Objective: The purpose of this meta-analysis was to evaluate the beneficial effects and optimal stimulation protocol of noninvasive brain stimulation (NIBS) including repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) on patients with mild cognitive impairment and Alzheimer disease. Materials and Methods: PubMed, Web of Science, Embase, and the Cochrane Library were searched until March 2020. The cognitive outcomes were extracted and the standardized mean difference with 95% confidence interval was calculated. Results: Twenty-eight studies were included. The result of NIBS showed significant effect on global cognition (P<0.05). Low-frequency rTMS over right dorsolateral prefrontal cortex (DLPFC), high-frequency rTMS (HF-rTMS) over left DLPFC, and the tDCS over left DLPFC and temporal lobe can significantly improve the memory function (P<0.05). HF-rTMS over left, right, or bilateral DLPFC can significantly improve the language function (P<0.05). Both HF-rTMS and tDCS over left DLPFC can obviously improve the executive function (P<0.05). Multiple sessions of rTMS with 80% to 100% intensity and anode tDCS with 2\u2009mA current density are more suitable for all these functions. Conclusions: NIBS has a beneficial effect on cognitive performance in both mild cognitive impairment and Alzheimer disease patients. Distinct optimal stimulation parameters were observed for different cognitive functions.