The effects of repetitive transcranial magnetic and transcranial direct current stimulation on memory functions in older adults with mild cognitive impairment: a systematic review and meta-analysis

Mengdie Hu; Michael A Nitsche; Yanxin Lv; Hairong Han; Xu Lin; Fengxue Qi

doi:10.3389/fnhum.2024.1436448

The effects of repetitive transcranial magnetic and transcranial direct current stimulation on memory functions in older adults with mild cognitive impairment: a systematic review and meta-analysis

Front Hum Neurosci. 2024 Aug 13:18:1436448. doi: 10.3389/fnhum.2024.1436448. eCollection 2024.

Authors

Mengdie Hu¹, Michael A Nitsche^{2

3

4}, Yanxin Lv⁵, Hairong Han⁶, Xu Lin⁷, Fengxue Qi⁵

Affiliations

¹ School of Sports Medicine and Rehabilitation, Beijing Sport University, Beijing, China.
² Department of Psychology and Neurosciences, Leibniz Research Center for Working Environment and Human Factors, Dortmund, Germany.
³ University Clinic of Psychiatry and Psychotherapy, Protestant Hospital of Bethel Foundation, University Hospital OWL, Bielefeld University, Bielefeld, Germany.
⁴ German Center for Mental Health (DZPG), Bochum, Germany.
⁵ Sports, Exercise and Brain Sciences Laboratory, Sports Coaching College, Beijing Sport University, Beijing, China.
⁶ Blood Purification Department, The Eighth People's Hospital of Jinan, Shandong, China.
⁷ Shandong Mental Health Center, Shandong University, Jinan, China.

Abstract

Mild cognitive impairment (MCI) is a condition that impairs activities of daily living, and often transforms to dementia. Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) show promise in improving cognitive functions in MCI patients. In this meta-analysis, we aimed to compare the effects of rTMS and tDCS on memory functions in MCI patients. We explored eight databases from their inception to March 16, 2024. We obtained 11 studies with 406 patients with MCI. We used the standardized mean difference (SMD) with a 95% confidence interval (CI) to synthesize the effect size. rTMS and tDCS significantly improved memory functions in MCI patients (SMD = 0.61; 95% CI: 0.41-0.82; p < 0.00001; I² = 22%). In subgroup analysis of number of stimulation sessions, both rTMS and tDCS over 10 sessions (SMD = 0.84; 95% CI: 0.50-1.17, p < 0.00001, I² = 0%) significantly improved the memory function in MCI patients. The subgroup analyses on different stimulation types (SMD = 0.78; 95% CI: 0.51-1.06; p < 0.00001; I² = 0%) and treatment persistent effects (SMD = 0.93; 95% CI: 0.51-1.35, p < 0.0001, I² = 0%) showed that rTMS was more effective than tDCS. rTMS with a stimulation frequency of 10 Hz (SMD = 0.86; 95% CI: 0.51-1.21; p < 0.00001; I² = 0%) and over 10 sessions (SMD = 0.98; 95% CI: 0.58-1.38; p < 0.00001; I² = 0%) at multiple sites (SMD = 0.97; 95% CI: 0.44-1.49; p = 0.0003; I² = 0%) showed a great improvement in the memory performance of patients with MCI. rTMS was more likely to appear temporary side effects (risk ratio (RR) = 3.18, 95% CI: 1.29-7.83, p = 0.01). This meta-analysis suggests that rTMS and tDCS are safe and efficient tools to improve memory functions in patients with MCI, while rTMS had a larger effect than tDCS. rTMS with a stimulation frequency of 10 Hz targeted on multiple sites over 10 sessions showed the greatest effect. We could not conclude parameters of tDCS because of insufficient data.

Systematic review registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42024558991.

Keywords: cognitive function; memory; mild cognitive impairment; non-invasive brain stimulation; repetitive transcranial magnetic stimulation; transcranial direct current stimulation.

Publication types

Systematic Review

Grants and funding

The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. This research was funded by the Fundamental Research Funds for the Central Universities (the Laboratory of Exercises Rehabilitation Science, 2023KFZX002), and the Research Foundation for Advanced Talents of Beijing Sport University (3101037).