Vagal Nerve Stimulation for Chronic Constipation: A Systematic Review and Meta-Analysis of Randomized Controlled...

Chronic constipation is a prevalent and heterogeneous disorder, affecting approximately 10% to 14% of adults and significantly influencing quality of life. Neuromodulation has been explored as a potential treatment; however, evidence remains limited. Therefore, this meta-analysis of randomized controlled trials (RCTs) aims to assess the efficacy and safety of vagus nerve-based neuromodulation techniques for chronic constipation, specifically transcutaneous auricular vagus nerve stimulation (taVNS) and transcutaneous electroacupuncture (TEA).

A comprehensive search of PubMed, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials was performed from inception to June 2025. Data were pooled using risk ratios for dichotomous outcomes and mean differences (MD) or standardized mean differences (SMD) for continuous outcomes, with 95% CIs, applying a random-effects model. Statistical analyses were conducted using R (version 4.4.2) in R-Studio, International Prospective Register of Systematic Reviews identification: (CRD420251132888).

Six RCTs involving 356 participants were included. Vagal nerve stimulation (VNS) significantly improved the visual analog pain scale (MD: -1.76 [95% CI: -2.92 to -0.60], p = 0.003), Bristol stool form scale (BSFS) (MD: 0.99 [95% CI: 0.30-1.68], p = 0.005), weekly spontaneous bowel movements (SBM) frequencies (MD: 1.75 [95% CI: 0.93-2.58], p < 0.0001), weekly complete spontaneous bowel movements (CSBM) frequencies (MD of 1.10 [95% CI: 0.40-1.80]), p = 0.002), and irritable bowel syndrome symptom severity (IBS-SSS) score (SMD of -1.68 [95% CI: -3.13; -0.24], p = 0.023). Still, there was no significant difference between the groups regarding Self-Rating Anxiety Scale (MD: -1.84 [95% CI: -6.19 to 2.52], p = 0.41), Self-Rating Depression Scale (SDS) scores (MD: -2.06 [95% CI: -6.14 to 2.02], p = 0.32), and anorectal function (p > 0.05).

VNS substantially improves VAS, BSFS, weekly SBM, weekly CSBM, and IBS-SSS scores.