Study design and setting
This prospective, multicenter, open-label clinical study was conducted between September 24, 2020, and February 22, 2022. The trial sites included Pok Oi Hospital‒The Chinese University of Hong Kong Chinese Medicine Clinic cum Training and Research Centre (Shatin District), and two community-based mobile clinics. The trial consisted of 8 weeks of treatment and 16 weeks of follow-up (an 8-week treatment period with follow-up at weeks 16 and 24). The trial was approved by the Joint Chinese University of Hong Kong‒New Territories East Cluster Clinical Research Ethics Committee (No. 2020.116) and registered in the Chinese Clinical Trial Registry (No. ChiCTR2000033650). The trial adhered to the Declaration of Helsinki and Good Clinical Practice guidelines. The study was conducted in accordance with the STandards for Reporting Interventions in Clinical Trials of Acupuncture recommendations . All participants provided written informed consent prior to participation. Treatments were provided free, and no subjects were paid for their participation.
Current smokers who wanted to quit smoking were recruited and underwent eligibility assessment by cross-referral from all Chinese medicine service units under the management of Pok Oi Hospital (covering all districts in Hong Kong) between September 2020 and August 2021.
Eligible participants had to meet the following inclusion criteria: (1) voluntarily quit smoking; (2) aged 18‒65 years; (3) smoked for ≥ 1 year; (4) consumed ≥ 20 cigarettes per day in the previous year; (5) positive salivary cotinine test; (6) nicotine dependence score (Fagerström Test for Nicotine Dependence, FTND ) of ≥ 4 points; (7) provided written informed consent and volunteered to participate; and (8) undergone a washout period of more than 1 month if other smoking cessation treatments were previously conducted.
Participants were excluded if they: (1) had severe and unstable cardiac, pulmonary, cerebral, or hematologic diseases or diabetes with other complications; (2) had mental illness or drug abuse; (3) had apoplexy or other nervous system diseases; (4) had unknown diseases; (5) had blood coagulation disturbances or were undergoing treatment with anticoagulant drugs; (6) had moderate or severe liver or kidney impairment; (7) were pregnant; or (8) had a history of smoking cessation treatments, such as acupuncture, auricular acupressure, or nicotine replacement therapy, within the previous month.
After eligibility assessment by the research team, the participants were enrolled and underwent baseline pretreatment evaluations. Routine biochemical and hematological tests and electrocardiography were performed before treatment administration.
All participants received standardized acupuncture and auricular acupressure treatments twice weekly for 8 consecutive weeks. The treatments were performed by Hong Kong Registered Chinese Medicine Practitioners who had over 3 years of practice experience and received training to execute standard protocol procedures prior to study initiation. The treatment protocol was developed based on the neural mechanism of acupuncture [6, 7], previous clinical studies [19, 20], and the clinical experience of acupuncture experts.
For acupuncture treatments, the acupoints Baihui (GV20), Yintang (GV29), bilateral Lieque (LU7), and bilateral Hegu (LI4) [21, 22] were used based on the methodology of an earlier smoking cessation study . During each treatment session, the participants were in a supine position exposing the acupoints. After skin disinfection, sterile, single-use acupuncture needles (0.25 mm × 25/40 mm; Suzhou Medical Appliance Factory, Suzhou, China) were inserted obliquely into GV20 (depth, 0.8–1.0 cun) and bilateral LU7 (depth, 0.5–1.0 cun until it reached Yangxi [LI5]), inserted transversely into GV29 (depth, 0.8 cun), and inserted perpendicularly into bilateral LI4 (depth, 0.5–0.8 cun). The needles were manipulated using the lifting and thrusting method  until deqi sensation  was achieved for each acupoint whenever possible, and retained in situ for 30 min before removal. During retention, the needles were manipulated by lifting and thrusting 20 times every 10 min.
Auricular acupressure was administered unilaterally, alternating between the left and right ear in each treatment session. The auricular acupoints used were Shenmen (TF4), Fei (CO14), Wei (CO4), Neifenmi (CO18), Pizhixia (AT4), Jiaogan (AH6a), and Kou (CO1) . After skin disinfection, Vaccariae seeds (Wang Bu Liu Xing) 2 mm in diameter were adhered with adhesive tape to the surface of the 7 auricular acupoints and maintained for 3 days. Participants were instructed to press each auricular acupoint via the central plastered seed 3–5 times per day for 30–60 s.
During the study period, the research team advised each participant to avoid any other treatments for smoking cessation but to continue medications for diseases such as hypertension, diabetes, hyperlipidemia, and coronary heart disease.
Evaluations in this study were performed at baseline and at weeks 2, 4, 6, and 8 after the start of treatment and again at weeks 16 and 24 when follow-up was performed.
The primary outcome measure was the success rate of smoking cessation at week 24. Success was defined as self-reported quitting and verified by an exhaled CO level < 10 parts per million (ppm) within 24 h of self-reported abstinence, measured using CO Check Pro (MD Diagnostics Ltd, Chatham, UK), and a negative test result for salivary cotinine, measured using the Oral Fluid Cotinine Test Mini Cube (TestCountry, San Diego, CA, USA).
Secondary outcomes were the success rates of smoking cessation at weeks 8 and 16, exhaled CO levels at each evaluation time point, efficacy indicators of the FTND and Autonomy Over Smoking Scale (AUTOS) at each evaluation time point, and scale evaluations of the Hamilton Anxiety Rating Scale (HAM-A), Self-rating Anxiety Scale (SAS), and Pittsburgh Sleep Quality Index (PSQI) at each evaluation time point. The FTND (score, 0–10) is a validated 6-item instrument devised to evaluate the number and strength of cigarettes smoked as well as smoking behavior, with higher scores indicating higher levels of nicotine dependence . AUTOS (score, 0–36) is a validated 12-item theory-based instrument with three subscales to assess withdrawal symptoms, psychological dependence, and cue-induced craving [26, 27]. HAM-A (score, 0–56) is a validated 14-item (symptom-defined elements) clinician-rated instrument for quantifying anxiety symptoms, with higher scores indicating greater symptom severity [28, 29]. The SAS (index, 25–100) is a validated 20-item rating instrument for anxiety disorders, with higher scores indicating greater anxiety . PSQI (score, 0–21) is a validated 19-item self-rated questionnaire for assessing sleep quality and disturbances, with higher scores indicating poorer sleep quality . Possible predictors for smoking cessation were evaluated, and all adverse events or reactions were monitored, appropriately managed, and recorded throughout the study period.
This study was part of the Guangdong-Hong Kong-Macau Greater Bay Area Smoking Cessation Project, and the Hong Kong site was assigned to recruit 30 subjects. Therefore, no additional formal sample size calculations were performed. This sample size is similar to that recommended by previous research on sample size determination for pilot trials .
We used the statistical package IBM SPSS Statistics version 27.0 (IBM Corp, Armonk, NY, USA) for conducting statistical analyses, and all participants’ data were included. Analyses were performed by a statistician not involved in treatment provision or data collection. All statistical tests were two-sided, with a significance level of 0.05.
To analyze the data, appropriate parametric or nonparametric statistical tests were used in accordance with the nature of the data. Baseline participant characteristics were reported as mean and standard deviation for continuous variables and as count and percentage for categorical variables.
To investigate changes in the mean scores for all continuous outcome variables from baseline to week 24, linear mixed-effects model (LMM) analyses were conducted. The fundamental assumptions of the LMM (including normality, validity of the model, and independence of data points) were tested to ensure the accuracy of the test results.
The overall and individual group changes for each continuous outcome from baseline across all measurement points were analyzed using LMM analyses. In addition, LMM analyses were performed to compare treatment effects between the successful and unsuccessful quit groups across all study time points from baseline to week 24 (group-by-time interaction effects). Post-hoc between-group and within-group differences were computed using the Bonferroni adjustment for multiple comparisons (six time points).
Furthermore, binary logistic regression was adopted to analyse the relationship between a series of baseline characteristics that could act as possible predictors and the success rate of smoking cessation at week 24 and was reported as odds ratio and 95% confidence interval (OR and 95% CI). Adverse events and additional information were descriptively analyzed and reported.