Transcutaneous auricular vagus nerve stimulation for sleep disorders: a systematic review and meta-analysis of sleep, anxiety, depression, and safety outcomes

Transcutaneous auricular vagus nerve stimulation (taVNS) is a promising non-invasive neuromodulation technique for treating sleep disorders (SD); however, its efficacy and safety have not been thoroughly evaluated. This study aims to provide more comprehensive and reliable evidence regarding the clinical application of taVNS for SD. 7 databases (PubMed, Embase, Cochrane Library, Web of Science, Scopus, CNKI, Wanfang) were systematically searched for randomized controlled trials (RCTs) investigating taVNS in the treatment of patients with SD. The search time range was from the establishment of the database to 10 January 2025. Effect measures were standardized mean differences, and effect sizes were expressed with 95% confidence intervals. A total of 14 RCTs were included, 11 of which were meta-analyzed. The meta-analysis showed that taVNS improved sleep quality (SMD =  -0.57, 95% CI = [-0.86, -0.28], p < 0.0001) , reduced fall asleep time (SMD =  -0.44, 95% CI = [-0.64, -0.23], p < 0.0001) and lowered depression- and anxiety-related scale scores (SMD =  -0.67, 95% CI = [-1.09, -0.25], p = 0.002; SMD =  -0.53, 95% CI = [-0.74, -0.32], p < 0.00001). Additionally, taVNS demonstrated a favorable safety profile, with only mild side effects. Most adverse events either resolved spontaneously or were effectively managed following treatment. Current evidence suggests that taVNS may improve sleep-related outcomes and appears to be generally well tolerated in patients with SD. However, given the heterogeneity across studies and the limited clinical interpretability of standardized effect sizes, these findings should be considered preliminary and require confirmation in larger, well-designed RCTs.