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. 2021 Jan 14:12:593000.
doi: 10.3389/fnagi.2020.593000. eCollection 2020.

Repetitive Transcranial Magnetic Stimulation for Improving Cognitive Function in Patients With Mild Cognitive Impairment: A Systematic Review

Lijuan Jiang  1 , Huiru Cui  1 , Caidi Zhang  1 , Xinyi Cao  1 , Nannan Gu  1 , Yikang Zhu  1 , Jijun Wang  1   2   3 , Zhi Yang  1   2   4   5 , Chunbo Li  1   2   3   4
Affiliations

Repetitive Transcranial Magnetic Stimulation for Improving Cognitive Function in Patients With Mild Cognitive Impairment: A Systematic Review

Lijuan Jiang et al. Front Aging Neurosci. .

Abstract

Background: Mild cognitive impairment (MCI) is an early stage of Alzheimer's disease. Repetitive transcranial magnetic stimulation (rTMS) has been widely employed in MCI research. However, there is no reliable systematic evidence regarding the effects of rTMS on MCI. The aim of this review was to evaluate the efficacy and safety of rTMS in the treatment of MCI. Methods: A comprehensive literature search of nine electronic databases was performed to identify articles published in English or Chinese before June 20, 2019. The identified articles were screened, data were extracted, and the methodological quality of the included trials was assessed. The meta-analysis was performed using the RevMan 5.3 software. We used the GRADE approach to rate the quality of the evidence. Results: Nine studies comprising 369 patients were included. The meta-analysis showed that rTMS may significantly improve global cognitive function (standardized mean difference [SMD] 2.09, 95% confidence interval [CI] 0.94 to 3.24, p = 0.0004, seven studies, n = 296; low-quality evidence) and memory (SMD 0.44, 95% CI 0.16 to 0.72, p = 0.002, six studies, n = 204; moderate-quality evidence). However, there was no significant improvement in executive function and attention (p > 0.05). Subgroup analyses revealed the following: (1) rTMS targeting the left hemisphere significantly enhanced global cognitive function, while rTMS targeting the bilateral hemispheres significantly enhanced global cognitive function and memory; (2) high-frequency rTMS significantly enhanced global cognitive function and memory; and (3) a high number of treatments ≥20 times could improve global cognitive function and memory. There was no significant difference in dropout rate (p > 0.05) between the rTMS and control groups. However, patients who received rTMS had a higher rate of mild adverse effects (risk ratio 2.03, 95% CI 1.16 to 3.52, p = 0.01, seven studies, n = 317; moderate-quality evidence). Conclusions: rTMS appears to improve global cognitive function and memory in patients with MCI and may have good acceptability and mild adverse effects. Nevertheless, these results should be interpreted cautiously due to the relatively small number of trials, particularly for low-frequency rTMS.

Keywords: cognitive function; meta-analysis; mild cognitive impairment; repetitive transcranial magnetic stimulation; systematic review.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Flowchart of the literature search and screening processes.
Figure 2
Figure 2
Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.
Figure 3
Figure 3
(A) Funnel plot for the publication bias of global cognitive function (B) Funnel plot for the publication bias of memory. SMD, standardized mean difference.
Figure 4
Figure 4
Forest plot of the comparison between the repetitive transcranial magnetic stimulation and control groups with respect to global cognitive function.
Figure 5
Figure 5
Meta-analysis forest plot of subgroup analysis showing global cognitive function of repetitive transcranial magnetic stimulation group vs. control group in the treatment of mild cognitive impairment: left hemisphere vs. right hemisphere vs. bilateral hemispheres.
Figure 6
Figure 6
Meta-analysis forest plot of subgroup analysis showing global cognitive function of repetitive transcranial magnetic stimulation group vs. control group in the treatment of mild cognitive impairment: treatment times ≥20 times vs. treatment times < 20 times.
Figure 7
Figure 7
Forest plot of the comparison between the repetitive transcranial magnetic stimulation and control groups with respect to memory.
Figure 8
Figure 8
Meta-analysis forest plot of subgroup analysis showing memory of repetitive transcranial magnetic stimulation group vs. control group in the treatment of mild cognitive impairment: left hemisphere vs. right hemisphere vs. bilateral hemispheres.
Figure 9
Figure 9
Meta-analysis forest plot of subgroup analysis showing memory of repetitive transcranial magnetic stimulation group vs. control group in the treatment of mild cognitive impairment: high frequency stimulation vs. low frequency stimulation.
Figure 10
Figure 10
Meta-analysis forest plot of subgroup analysis showing memory of repetitive transcranial magnetic stimulation group vs. control group in the treatment of mild cognitive impairment: treatment times ≥20 times vs. treatment times < 20 times.
See this image and copyright information in PMC

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