Effects of Auricular Stimulation on Inflammatory Parameters: Results of a Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background: The number of randomized controlled trials (RCTs) using auricular stimulation (AS) techniques, such as transauricular vagus nerve stimulation, auricular electrostimulation, auricular acupuncture, and acupressure in experimental and clinical settings has increased markedly over the last three decades. This systematic review evaluates the effects of AS on biomarkers of inflammation and stress responses.

Materials and methods: The following data bases were searched: MEDLINE (PubMed), EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), ISI Web of Science, and Scopus Data base. Data collection and analysis were conducted independently by two reviewers. Quality and risk assessments of the included studies were performed, and a meta-analysis of the effects of the most frequently assessed biomarkers was conducted using RevMan statistical software.

Results: A total of 1122 patients and healthy volunteers from 27 RCTs were included in this systematic review; 81% of the participants were female, with a median age of 51 years. Pooled data of 18 studies showed a significant effect of AS regarding a reduction of serum C-reactive protein, tumor necrosis factor-α, interleukin (IL)-6, and IL-10. Although IL-4, IL1β, cortisol, substance P and calcitonin gene-related peptide, and adrenocorticotropic hormone did not show any changes, salivary amylase increased under AS.

Conclusions: The influence of inflammatory cytokines seems to be mediated by AS. More research is needed to investigate the effects of AS on the immunologic system in addition to its clinical significance in high-quality RCT.