Efficacy of transcranial alternating current stimulation on cognitive function in patients with dementia: a systematic review and meta-analysis of randomized controlled trials.

Abstract

Background: Transcranial alternating current stimulation (tACS) has shown potential for improving cognitive function in dementia, but evidence remains inconsistent. This systematic review and meta-analysis aims to evaluate the efficacy of tACS on cognitive function in dementia.

Methods: We searched seven databases for randomized controlled trials (RCTs) assessing tACS effects on cognitive function in dementia. Two reviewers independently screened the literature, extracted data, and assessed study quality. A random-effects model was used to calculate standardized mean differences (SMDs) with 95% confidence intervals (CIs). GRADE was used to rate evidence quality.

Results: A total of 9 RCTs involving 357 patients with dementia were included. Compared with sham stimulation, tACS significantly improved immediate global cognition (SMD = 0.28; 95% CI [0.01, 0.54]; p = 0.04, I² = 39%), but not at follow-up. tACS also significantly improved immediate recall, delayed recall, and associative memory. Additionally, tACS significantly enhanced cholinergic transmission as measured by short-latency afferent inhibition (MD = 0.34, p < 0.001, I² = 0%). However, no significant effect was observed for neuropsychiatric symptoms, and the evidence for executive function was inconclusive. No serious adverse events occurred.

Conclusion: tACS may improve immediate global cognition and memory in patients with dementia, but no significant benefit was observed at follow-up or for neuropsychiatric symptoms. Findings are limited by few studies, heterogeneous parameters, and insufficient follow-up data. Future large, well-designed RCTs with standardized protocols are needed to optimize tACS parameters and confirm sustained efficacy.