Abstract
Earlier clinical trials have investigated the efficacy of auricular stimulation for hypertension, but the overall evidence regarding the effect of non-invasive auricular stimulation on blood pressure (BP) reduction remains unclear. This systematic review summarizes the effects of non-invasive auricular stimulation on cardiovascular haemodynamics. We searched for studies published in English through PubMed, ICHUSHI, and Cochrane Central Library databases and reviewed randomized controlled trials involving adults. Data collection and analysis were performed on the relationships of non-invasive auricular electrical stimulation and acupressure with changes in haemodynamics. A meta-analysis was conducted on the effects of non-invasive auricular stimulation on systolic BP (SBP), diastolic BP (DBP), and heart rate (HR). In the primary analysis, effect sizes were extracted from 18 studies for a total analytic sample of n = 959. Non-invasive auricular stimulation significantly reduced in SBP [weighted mean difference (WMD) = -4.435 mmHg, 95% confidence interval (CI) (-7.037 to -1.832)], DBP [WMD = -2.212 mmHg, 95% CI (-3.734 to -0.690)], and HR [WMD = -3.069 beats/min, 95% CI (-5.389 to -0.749)]. Overall, heterogeneity in each analysis was high, which could be explained by the stimulation duration and baseline values of SBP, DBP, and HR. There were no serious adverse events across all 18 studies. Enhancing vagus nerve activity through non-invasive auricular stimulation leads to clinically safe reductions in BP and HR. Further studies are needed to clarify whether non-invasive auricular stimulation can be used as a viable treatment for hypertension.