The safety and efficacy of gamma frequency auditory and visual stimulation in the treatment of alzheimer's disease: a systematic review and meta-analysis.

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with cognitive decline and significant global health burden. Current treatments offer limited benefits, highlighting the need for novel therapies. Gamma-frequency auditory and visual stimulation (GFAVS), utilizing 40 Hz neuromodulation, has gained attention as a non-invasive treatment for cognitive deficits and underlying pathophysiology in AD.

OBJECTIVE

This systematic review and meta-analysis aimed to assess the safety and efficacy of GFAVS in treating Alzheimer's disease (AD) and mild cognitive impairment (MCI).

METHODS

A comprehensive literature search across multiple databases (PubMed, Cochrane Library, MEDLINE, Web of Science, and Embase) was performed up to November 2025. Controlled trials involving adults (≥50 years) with AD or MCI, using GFAVS, were included. Meta-analyses assessed adverse events, cognitive function, and brain changes.

RESULTS

Eleven studies (341 participants) were included. GFAVS was safe, with no significant increase in overall adverse events (RR = 0.99, P = 0.93; RD = -0.01, P = 0.93). However, GFAVS significantly increased the risk of tinnitus (RR = 6.46, P = 0.08; RD = 0.16, P = 0.01). GFAVS significantly improved structural brain changes (SMD = 1.74, P = 0.02), especially in mixed AD and MCI populations (SMD = 3.05, P < 0.00001). Nevertheless, no significant improvements were observed in cognitive function (SMD = 0.16, 95% CI [-0.36 to 0.68], P = 0.55) or activities of daily living (SMD = 0.53, 95% CI [-1.26 to 2.33], P = 0.56), despite the observed structural brain changes. High heterogeneity was observed.

CONCLUSION

GFAVS appears to be well tolerated and may induce structural brain alterations in individuals with Alzheimer's disease or mild cognitive impairment; however, its impact on cognition or daily functioning remains to be established. Large-scale, rigorously designed trials are required to clarify optimal protocols and address the observed heterogeneity.