The effect of long-term non-invasive vagus nerve stimulation on cognitive performance: results from a randomized placebo controlled trial

Abstract Vagal withdrawal may play an etiological role in cognitive impairment. The efficacy of a non-invasive transcutaneous vagus nerve stimulation (tVNS), an intervention that should have a direct influence on brain systems underlying cognitive function is unknown. We tested the effect of daily tVNS administered for 2 weeks on cognitive function. Here we present first results from chosen 4 cognitive tests. Participants were 68 men and women aged 18 to 75 years who were randomised into four groups: early and sham tVNS and late and sham tVNS. Early groups underwent daily 4hr stimulation between Day 0 and 13, while late groups underwent daily 4hr stimulation between Day 14 and 28. tVNS was applied on the left tragus, and sham tVNS was applied on the left earlobe. Cognitive measures were cumulative score of 4 executive function tests (NIH Examiner- Flanker, SetShift, Nback/2Nback) and immediate recall (Rey´s Auditory Verbal Learning test). Analysis of prespecified contrasts, revealed that executive function improved in all groups similarly and that there were no differences in change by placebo or actual stimulation groups. For immediate recall, there were significant improvements for actual tVNS groups between Day 0 and Day 13 in the early stimulation phase (p =0.02), and between Day 14 and Day 28 in the late phase (p = 0.01). No such difference was found in sham tVNS groups applied early and late (p = 0.82 and p = 0.67). We found that tVNS applied daily improved immediate recall but not executive function. Our first results suggest that transcutaneous vagus nerve stimulation may have a potential beneficial effect on memory but not executive function. Research Category and Technology and Methods Basic Research: 12. Vagus Nerve Stimulation (VNS) Keywords: cognition, transcutaneous vagus nerve stimulation, long-term intervention, randomized placebo controlled