Background: The number of randomized controlled trials using auricular stimulation (AS) such as transauricular vagus nerve stimulation, or auricular electrostimulation or auricular acupuncture or acupressure, in experimental and clinical settings has increased markedly over the last three decades. Various clinical scores and self-reported outcomes are used as primary outcome measures to evaluate the effects of AS; they have been already analysed in an array of systematic reviews. But regarding the effect of AS on objective, physiological measures (biomarkers), for example blood values, heart rate, electrophysiological measurements and brain imaging, a systematic analysis is missing. This systematic review protocol was developed following the PRISMA guidelines to explore and evaluate for the first time the existing literature examining the impact of AS on biomarkers in randomized controlled trials as reported in their primary or secondary outcomes.
Methods and analysis: The following databases will be searched: MEDLINE (PubMed), EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), ISI Web of Science, and Scopus Database. RCTs will be included if an abstract is available in English. Data collection and analysis will be conducted by two reviewers independently. Quality and risk assessment of included studies will be done using the Cochrane 6.1.0 handbook criteria and RoB 2 tool and meta-analysis of the effect of the most frequently assessed biomarkers will be conducted using the statistical software RevMan V.5.3.
Ethics and dissemination: This systematic review will evaluate the effect of AS and related techniques on various blood values and physiological measures. Since all data used in this systematic review and meta-analysis will have been published, this review does not require an ethical approval. The results will be published in a peer-reviewed journal as well as presented in relevant conferences.
Registration number: PROSPERO CRD42021231885