Acoustic stimulation for sleep enhancement and declarative memory: A systematic review and meta‐analysis

Background Acoustic stimulation is a non‐invasive neuromodulation approach with unclear efficacy for sleep and cognition across paradigms and populations. This meta‐analysis systematically evaluated its effects on sleep architecture and declarative memory. Methods We searched the PubMed, Web of Science, the Cochrane Library, Scopus, and Embase databases up to 16 June 2025, for randomized controlled trials (RCTs) and high‐quality non‐randomized controlled trials (NRCTs). Risk of bias was assessed with Cochrane RoB 2 and ROBINS‐I. Meta‐analyses were performed using RevMan 5.4 and STATA 18.0, calculating mean difference (MD) or standardized mean difference with 95% CIs; crossover trials used paired analysis. Results Sixteen RCTs and one NRCT (440 participants) included. Acoustic stimulation showed no significant effect on total sleep time (MD = 1.81 minutes), 95% CI [−3.14, 6.75], WASO MD = −2.56 minutes, 95% CI [−5.80, 0.67], or SWS duration (MD = 0.89 minutes, 95% CI [−5.29, 7.07]). Declarative memory recall showed no significant improvement (MD = 1.35 points, 95% CI [–3.75, 6.45]). Conclusions Current pooled RCT evidence does not support consistent beneficial effects of acoustic stimulation on sleep or declarative memory. Although qualitative synthesis suggests potential modulation of sleep microstructure, findings are preliminary due to substantial heterogeneity, limited sample sizes, and methodological inconsistencies. Future research should prioritize standardized protocols and personalized closed‐loop paradigms to validate therapeutic potential.