Hypertension, a worldwide public health problem, is a major risk factor for cardiovascular and kidney disease. The prevalence and global burden of the disease are increasing . Stage 1 hypertension is systolic blood pressure (SBP) varying from 140 to 159 mmHg or diastolic blood pressure (DBP) varying from 90 to 99 mmHg, and it is a common form of hypertension. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC7) defined prehypertension as SBP of 120 to 139 mmHg and DBP of 80 to 89 mmHg to identify individuals who were associated with a risk of developing hypertension and decrease blood pressure (BP), inhibit the progression of BP to hypertensive levels with age and prevent hypertension through early intervention .
The current treatments for hypertension include several classes of antihypertensive drugs and strategies to modify the effect of adverse lifestyles on blood pressure. Non-pharmacological interventions, including weight loss, reduced sodium intake, regular physical activity, smoking cessation, and the moderation of alcohol intake, are recommended [2, 3]. Antihypertensive drugs, including angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), beta-blockers, calcium channel blockers (CCBs), and thiazide-type diuretics, are commonly used . However, it is still controversial whether antihypertensive drug therapy is needed for persons with prehypertension [4, 5] and mild hypertension [6, 7]. Long-term compliance with lifestyle modifications is also difficult for the patient.
Acupuncture has been widely used to treat various conditions, including cardiovascular disease and hypertension . The mechanisms underlying the BP-lowering effect of acupuncture are associated with the control of BP modulators such as renin , aldosterone , angiotensin II  and endothelin-1 , and neurotransmitter modulation such as glutamate, GABA, serotonin and endocannabinoids . Of three high-quality, randomised, controlled trials, two showed a positive effect on BP [14, 15], but one trial reported a non-significant BP reduction between the groups . Auricular acupuncture is one type of acupuncture based on the understanding that the external ear represents all parts of the human body, including the internal organs, and provides acupuncture points corresponding to these parts [17, 18]. Several articles have evaluated the effect of auricular acupuncture on controlling BP [19–22]. Some studies also reported that the electroacupuncture treatment of auricular acupoints decreased BP in patients with hypertension [23, 24]. However, the scientific evidence is insufficient . Most previous studies have some methodological limitations, including low quality of the study design, small sample size, inadequate control groups, and a lack of suitable outcome measures. In addition, there is no clinical trial evaluating the effect of auricular acupuncture on prehypertension. Safe and effective interventions that are able to manage pre/mild hypertension would be desirable. Therefore, more rigorous studies are needed to elucidate the effect and safety of auricular acupuncture on pre/mild hypertension.
In the present study, we aimed to perform a randomised controlled clinical trial in patients with prehypertension and stage 1 hypertension to evaluate the effect and safety of auricular acupuncture compared with usual care. The 24-h ambulatory blood pressure will be used as the primary endpoint. The results derived from this study will also be used to explore the feasibility of auricular acupuncture treatment and calculate the appropriate sample size for a future large clinical trial.