Influence of 2-week auricular transcutaneous vagus nerve stimulation on memory: findings from a randomized trial in community-dwelling adults

Abstract

Background Memory plays an essential role in daily life and is one of the first functions to deteriorate in cognitive impairment and dementia. Transcutaneous vagus nerve stimulation (tVNS) is a promising therapeutic method, however its ability to enhance memory is underexplored, especially considering long-term stimulation. We aimed to investigate the effect of a 2-week course of auricular tVNS (atVNS) on memory in apparently healthy adults. Methods In the single-blind randomized placebo-waitlist control trial 76 participants (men = 30; mean age = 48.32) were recruited and randomized into four groups: EARLY ACTIVE or SHAM atVNS and LATE ACTIVE or SHAM atVNS. Participation in the study lasted 4 weeks where EARLY groups underwent 2 weeks intervention immediately following the first study site visit (days 0 to 13) and LATE groups 2 weeks after the first study site visit (days 14 to 27). ACTIVE and SHAM atVNS included 2 weeks of daily 4 hours of neurostimulation at the tragus or earlobe, respectively. To assess memory, we used the Rey Auditory Verbal Learning Test. Results Two weeks of ACTIVE atVNS, but not SHAM atVNS improved immediate recall and short-term memory score both in EARLY and LATE groups. Furthermore, the improvements persisted over subsequent follow-up in EARLY ACTIVE atVNS. Importantly, the effect of ACTIVE atVNS was superior to SHAM for immediate recall in both EARLY and LATE groups. There were no significant changes in delayed recall. Conclusion Our findings suggest that atVNS improves memory, particularly immediate recall and may be an effective method in preventing memory loss and mitigating cognitive aging.