Effect of transcutaneous auricular vagus nerve stimulation on the improvement of cognitive function in older patients with schizophrenia: A randomised controlled study

Aims: To investigate the efficacy and safety of transcutaneous auricular vagus nerve stimulation (taVNS) in improving cognitive function in older inpatients with schizophrenia. Design: Randomised controlled trial. Setting: Cognitive improvement in hospitalised older patients with schizophrenia in Shanghai. Participants: Fifty-one older inpatients with schizophrenia in Shanghai Mental Health Center. Intervention: The taVNS electrodes were placed on the skin with vagus nerve distribution in the taVNS group, whereas the electrodes were placed on the skin without vagus nerve distribution in the sham taVNS group. taVNS parameters included 25 Hz, the maximum tolerated current intensity (apparatus maximum load current ≤ 6 mA) and one 30-min session per day for 2 weeks, for a total of 10 interventions. Measurements: The primary outcome was a neurocognitive assessment. Safety was the secondary outcome measure. After each treatment session, adverse reactions were assessed using the self-administered Adverse Reaction Assessment Scale. Four subtests of the Cambridge Neuropsychological Test Automated Battery were further considered: reaction time (RTI), paired associate learning (PAL), multitasking test (MTT) and spatial working memory (SWM). Results: < 0.001). Compared to the sham taVNS, taVNS improved SWM performance in older patients with schizophrenia. Furthermore, the SWM performance after a single session of taVNS showed fewer errors in the taVNS group, whereas no such improvement was observed in the sham taVNS group. Unlike in SWM, there were no significant between-group differences in RTI, PAL or MTT after either a single stimulation or a session of 10 stimulations. Conclusions: taVNS may have the potential to improve SWM in older patients with schizophrenia.