The role of noninvasive brain stimulation for behavioral and psychological symptoms of dementia: a systematic review and meta-analysis

Objective This meta-analysis aimed at evaluating and comparing the efficacy of noninvasive brain stimulation (NIBS) techniques on the behavioral and psychological symptoms of dementia (BPSD). Methods An exhaustive literature retrieval was performed on PubMed, Embase, Cochrane Library, and Web of Science until October 2019. The primary outcome was the relative changes in BPSD severity scores immediately after NIBS and at the last follow-up visit. Subgroup analyses were conducted to compare the efficacy of repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS). Changes in the severity scores after NIBS were also analyzed with restriction to patients with Alzheimer’s disease (AD). Results Ten studies with 324 patients were included, out of which 7 studies involved patients with AD. The analysis results indicated that NIBS significantly improved the BPSD outcome immediately after stimulation (SMD, 0.31; 95% CI, 0.10–0.52; P = 0.005), but not at the last follow-up visit (0.15; − 0.11–0.41; 0.25). Our subgroup analyses suggested that the favorable effects of rTMS remained significant at the last follow-up visit (0.57; 0.18–0.96; 0.004). This discrepancy maybe caused by the continuously insignificant outcomes of tDCS on the whole data. The results for AD patients immediately after stimulation (0.37; 0.12–0.61; 0.003) and at the last follow-up visit (0.29; − 0.19–0.76; 0.24) were both largely similar to those in the whole patient group with dementia. Conclusions rTMS, rather than tDCS, was capable of persistently improving the BPSD at an early stage after treatment. More trials are warranted to confirm our results before the establishment of final conclusions.