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

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.