A systematic review and meta-analysis on the characteristics of transcranial magnetic stimulation treatment protocols for patients with Alzheimer's disease

Background Alzheimer's disease (AD) is the most common neurodegenerative condition causing dementia. Currently, there has been no established non-pharmacological treatment for cognitive decline in patients with AD. Recent evidence suggests that repetitive transcranial magnetic stimulation (rTMS) may be effective as a non-invasive treatment for improving cognitive function in AD. Objective This study aimed to examine the characteristics of rTMS treatment protocols for patients with AD Methods We conducted a systematic literature search on clinical trials on rTMS for improving cognitive decline in patients with AD, using the PubMed, PsycINFO, and Scopus databases and performed a meta-analysis according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. To clarify which cognitive domains in AD are improved by rTMS, meta-analyses were conducted on both global cognitive function and on each cognitive domain including verbal memory, processing speed, and executive function. In addition, sub-analyses of the treatment details of rTMS parameters including stimulation sites, stimulation frequency, stimulation intensity, and with/without the neuro-navigation technique and meta-regression analyses adjusting for gender, education, and the number of rTMS pulses were performed. Results The results showed significant improvements in global cognitive function, while no significant findings in verbal memory, processing speed and executive function. No significant results were found in subgroup analysis or meta-regression. Conclusions To enrich the evidence for cognitive enhancement in AD with rTMS, the randomized controlled trials using a unified rTMS protocol with a larger sample size are warranted.