Transcutaneous auricular vagal nerve stimulation improves functional dyspepsia by enhancing vagal efferent activity
Objectives: This study was designed to investigate whether transcutaneous auricular vagal nerve stimulation (taVNS) would be able to improve major pathophysiologies of functional dyspepsia (FD) in patients with FD. Methods: Acute: Thirty-six FD patients (21F) were studied in two sessions (taVNS and sham-ES). Physiological measurements, including gastric slow waves, gastric accommodation and autonomic functions, were assessed by the electrogastrogram (EGG), a nutrient drink test and the spectral analysis of heart rate variability derived from the electrocardiogram (ECG), respectively. Chronic: Thirty-six FD patients (25F) were randomized to receive 2-week taVNS or sham-ES. The dyspeptic symptom scales, anxiety and depression scores and the same physiological measurements were assessed at the beginning and the end of the 2-week treatment. Results: Acute: In comparison with sham-ES, acute taVNS improved gastric accommodation (p=0.008), increased the percentage of normal gastric slow waves (%NSW, fasting: p=0.010; fed: p=0.007) and vagal activity (fasting: p=0.056; fed: p=0.026). Chronic:In comparison with baseline, 2-week taVNS but not sham-ES reduced symptoms of dyspepsia (p=0.010), decreased the scores of anxiety (p=0.002) and depression (p<0.001), improved gastric accommodation (p<0.001) and the %NSW (fasting: p<0.05; fed: p<0.05) by enhancing vagal efferent activity (fasting: p=0.015; fed: p=0.048). Compared with the HC, the patients showed increased anxiety (p<0.001) and depression (p<0.001), and decreased gastric accommodation (p<0.001) and %NSW (p<0.001) as well as decreased vagal activity (fasting: p=0.047). Conclusions: The noninvasive taVNS has a therapeutic potential for treating non-severe FD by improving gastric accommodation and gastric pace-making activity via enhancing vagal activity.