Ameliorating Effects and Autonomic Mechanisms of Transcutaneous Auricular Vagus Nerve Stimulation on Abdominal Pain in Patients With Functional Dyspepsia and Irritable Bowel Syndrome.
BACKGROUND: Patients with functional dyspepsia (FD) and irritable bowel syndrome (IBS) often experience abdominal pain and reduced quality of life and need effective treatments. This exploratory study aimed to evaluate whether transcutaneous auricular vagus nerve stimulation (taVNS) could improve abdominal pain and quality of life in patients with FD and IBS, and whether the effects were mediated via the autonomic mechanisms. METHODS: A total of 64 patients with abdominal pain (43 FD and 21 IBS) with a pain score of 3 out of 10 or higher were randomized to receive 2 weeks of taVNS or sham-taVNS treatment. The primary outcome was numeric rating scale (NRS) for abdominal pain. The dyspeptic symptom scales (DSS), IBS symptom severity scale score (IBS-SSS), anxiety and depression scores, and the SF36 quality of life scale were assessed before and after the treatment. The electrocardiogram was also recorded for the assessment of autonomic function at baseline and after the treatment. KEY RESULTS: (1) taVNS reduced the abdominal pain score (p < 0.001 for both FD and IBS), the frequency of abdominal pain (p < 0.001 for both FD and IBS), and overall symptom scores in both FD patients and IBS patients (p < 0.001 for FD and IBS). There was no significant difference in the effect of taVNS on abdominal pain between FD and IBS patients. (2) taVNS improved quality of life compared with baseline in both FD and IBS patients. (3) taVNS decreased anxiety (p < 0.001) and depression (p < 0.001). (4) taVNS increased vagal activity. At the end of the taVNS treatment, the vagal activity was negatively correlated with the pain score (r = -0.491, p = 0.004). CONCLUSIONS: Non-invasive taVNS improves abdominal pain, quality of life, and anxiety and depression in patients with FD and patients with IBS, possibly attributed to the enhancement of vagal activity. TRIAL REGISTRATION: Chinese Clinical Trial Registry: ChiCTR2400085697.