Studies in the general population indicate that one-third of adults in Western countries experience difficulty with sleep initiation or maintenance at least once a week and 6–15% are thought to meet criteria of insomnia in that they report sleep disturbance as well as significant daytime dysfunction. The prevalence is even higher in older people and twice as high in women as in men. Daytime complaints of people with insomnia concern cognitive functioning , depressed mood and fatigue. Additionally, people reporting insomnia or low sleep quality have higher risks of depression, anxiety and irritation, metabolic diseases and cardiovascular problems. Though it is not a life threatening disorder, these daytime consequences and comorbidities lead to a reduction in work productivity, to increased sick leave and healthcare consumption and consequently to high economic costs.
Acupuncture has been practiced in China for more than 3,000 years. The rapid development of acupuncture over the last few decades has itself led to great innovations in practice. Auricular acupuncture, an important branch of acupuncture, has been widely used in a variety of disorders. Previous studies have exhibited that taVNS is an effective treatment for some diseases, like depression, epilepsy and diabetes. Moreover, stimulation at the auricular branch of vagus nerve can trigger melatonin secretion, which may improve the symptoms of insomnia.