Complementary and alternative medicine (CAM) refers to diverse health care practices and products that are not currently considered as part of traditional medicine such as acupuncture, aromatherapy, Qi-gong, and herbalism [1]. Attention to CAM has increased rapidly worldwide since the 1990s and the World Health Organization has been developing the “Traditional Medicine Strategy” to strengthen the health care system by integrating traditional medicine and CAM since 2002[2]. According to a systematic review of 49 relevant studies, the rate of CAM use has increased up to 76% regardless of the types, definitions, and durations of CAM therapies [3,4].

Auriculotherapy, classified as a type of acupuncture, is a physical reflex therapy stimulating the specific ear points matched to parts of the body with physical or psychological symptoms using needles, magnets, or seeds [5,6]. The mechanism of auriculotherapy is closely related to the meridian theory, which states that the pathological changes in the organs of the human body appear on the surface of the ears when the meridians lose their balance [6]; thus, examining ears help diagnose problems in the in-ternal organs, and symptoms can be alleviated by stim-ulating reflex points in the ears that correspond to the organs. Auriculotherapy is considered safer than other CAM therapies such as body acupuncture, moxibustion, and cupping. Additionally, non-invasive methods of auriculotherapy using seeds or pellets are most commonly used because they could eliminate the fear of needles and reduce the risk of infection and bleeding [6,7].

The effects of auriculotherapy on fever, sciatica, and even birth control have been reported in ancient China, Egypt, Greece, and Rome [4,5]. Several studies investigated its effectiveness in a wide variety of areas including pain control [8], obesity [9], sleep disorders [10], and symptoms related to cancer treatment [11]. Nursing researchers also began to explore the effects of auriculotherapy in 2000 and then expanded the target areas and detailed methods of auriculotherapy between 2006 and 2010[12], which increased the necessity for the systematized review of the interventions using auriculotherapy. However, most reviews had more interest in the effects of auriculotherapy on a specific symptom such as pain [7,11], obesity [9], insomnia [10] than the detailed methods of the interventions. Furthermore, no other reviews analyzed the methods of auriculotherapy according to the standardized reporting guideline although the heterogenous way of reporting on the interventions of previous studies has posed difficulty to better understand and interpret results of the intervention using auriculotherapy.

The STandards Reporting Interventions in Clinical Trials of Acupuncture (STRICTA), an international acupuncture research group, has provided authors with reporting guidelines for clinical results in non-pharmacological CAM intervention since 2001, which suggested it is necessary to report details on key components of interventions; acupuncture treatment, needling details, practitioner background, treatment regimens, other components of the treatment, and interventions for control group in research studies [13,14].

Therefore, this study aimed to identify research trends in auriculotherapy published in Korea in the past 10 years and systematically analyze the characteristics and types of auriculotherapy performed according to the STRICTA guidelines.

This study extracted Korean publications on studies that applied auriculotherapy in the past 10 years, using 6 keywords and 4 literature search databases, and analyzed the intervention details according to the STRICTA guidelines.

Seventy-eight studies on auriculotherapy in the past 10 years showed a consistently increasing trend, from 15 studies between 1991 and 2000 to 56 studies between 2001 and 2010[12]; the intervention and outcomes variables were also diversified. Among the previous studies in the nursing discipline, most (45.5%) were related to insomnia and limited to six areas (e.g., menstruation syndromes, quitting smoking, obesity, headache, and anxiety). However, the area of auriculotherapy expanded to management of chronic diseases such as blood pressure or diabetes, and various symptoms besides the six areas during the recent 10 years. The popularization of CAM in Korea can explain this result. A survey on Korean female and male adult samples in 1999 showed that only 26% of the respondents used CAM [15], while a recent study in 2019 reported that 81% use CAM therapies for promoting health status and building a positive body image [16]. Particularly, CAM use has extended to the younger people in their 20s and 30s through the spread of information via the internet and mass media in contrast to the frequent use of CAM by the middleaged generation as home remedies in the past [16]. As the rate of CAM use is thus expected to continue to rise, the variability in the studies using auriculotherapy will increase.

Regarding study design, the quasi-experimental design was most commonly used, consistent with a previous study that analyzed research trends in nursing in Korea [17]. Notably, studies using a true experimental design showed an increase to 15.4%. According to a previous study, the number of studies using a quasi-experimental design consistently increased among all research studies conducted in the field of nursing from 1991 to 2000 while the true experimental design showed a decreasing trend from 9.0% to 3.7% between 2001 and 2010[17]. Furthermore, considering that only 5.6% of studies had a true experimental design in another previous study analyzing the research trends of auriculotherapy between 1991 and 2010 in Korea [12], this result showed that there was substantial qualitative growth of auriculotherapy research in the past 10 years. Given the controversies on the quality of studies on CAM, the in-creasing number of true experimental studies that pro-vided a high standard of evidence can contribute to estab-lish the efficacy and safety of auriculotherapy. However, as for the control interventions, approximately the half of the studies used experimental design with no-treatment control group, which could not rule out the placebo effect. Hence, intervention studies with an active control group is needed to effectively rule out the placebo effect and prove the superior effect of auriculotherapy [18].

We also found that the nursing discipline conducted intervention studies for the patients in 13 studies, while only 18 studies were on the symptoms of people with disease or symptoms across all the disciplines, which showed the usefulness of auriculotherapy as a nursing intervention. This result can be explained as follows. First, the perspectives of auriculotherapy and nursing are similar. The importance of seeing and nursing a person from an integrated perspective has been discussed since the 1970s in the nursing discipline [19]. This is similar to the perspective and philosophical context of auriculotherapy, which states that human organs represent a single entity and require a holistic treatment [5,6]. Thus, it can be inferred that auriculotherapy can be easily applied to patients as a nursing intervention. Second, the low level of adverse effects is an important consideration for selecting and applying auriculotherapy as a nursing intervention. As shown in the results of this study, the main cause of dropouts was personal reasons, and only 9.6% and 5.4% of the experimental group and control group, respectively, dropped out owing to adverse effects. In the experimental group, nine people across seven studies reported nausea, pain, and discomfort, and in the control group, six people across six studies dropped out due to the same reasons; however, no serious adverse effects were reported. These results are in line with those from a systematic review reporting nausea, pain, irritation on the skin area of intervention, and discomfort as the adverse effects of auriculotherapy [7]. Therefore, prior education about the predictable problematic symptoms and efforts to increase safety through continued observation can establish auriculotherapy as a more safely applicable nursing intervention method.

As for the treatment regimen, the buried therapy was most frequently used. Buried therapy, which is a non-invasive method, has a reduced risk of infection compared to the invasive method of acupuncture therapy, thus reducing complications. Additionally, level of pain during treatment is relatively low, thus reducing the dropout rate. Vaccaria seeds are widely used because they are known to have a warm characteristic, they are nontoxic, and help to augment flow of the Qi [20]. Meanwhile, there were inconsistent results on the effectiveness of the types of needle used in auriculotherapy. A study to compare the effect of two different types of auriculotherapy applied for shoulder pain in Korean female adults reported that the experimental group using Sinban stone had significant pain relief when compared with the control group that used acupressure pellet [21]. Additionally, a study on teenagers with BMI over 23 showed that the group that used magnetic pearls had a greater reduction in BMI when compared with the one that used Vaccaria seeds [22]. On the contrary, a study on pain reduction during the endoscopic examination of large intestine indicated that auriculotherapy reduced pain but did not show any differences between the use of Vaccaria seeds and the transcutaneous auricular stimulation [23]. For better implementation of auriculotherapy, further studies should be conducted to compare the effects depending on needle types used in auriculotherapy.

In line with the results of previous literatures indicating that the appropriate auriculotherapy period is less than five days per treatment [5,6], we found that the preferred frequency of intervention session was once a week including a cessation time of two days. Several studies reported that appropriate cessation was important to prevent the risk for skin damage, infection, and any allergic reactions caused by the seeds, and tapes used for non-invasive type of auriculotherapy [5–7,24]. This result might help to decide the effective dose of treatment with decreased risk for adverse effects when applying long-term auriculotherapy intervention in the future study.

Additionally, the intervention period in the previous trend analysis was “less than one week” and “between one week and one month” in 33.8% each [12]. In contrast, the results of this study showed that the duration of intervention has been extended to more than a month in 42.7% of the studies. The changing trend of the outcome variables can be related to this result. From the 1990s to 2010, auriculotherapy had been usually limited to quitting smoking, relieving sleep disturbances and menstruation syndromes. On the contrary, outcome variables applied were diversified in the last 10 years. Furthermore, we analyzed the treatment regimen including the sessions, days, and time of cessation of the intervention and tried to compare it with the existing data. However, no previous study has examined these aspects, and thus, no direct comparison was possible. Therefore, it will be necessary to identify which intervention method is more effective depending on the disease and condition for which auriculotherapy is applied by conducting a systematic review based on the results of this study.

Quality intervention requires systematic reporting that can reduce ambiguity and increase the reliability and ap-plicability of the results by providing evidence for decision-making regarding the intervention method [14]. However, several studies on auriculotherapy did not report the detailed information on the intervention as suggested by the STRICTA. Specifically, the patients' backgrounds were unclearly or nonspecifically described in 54.7% and information on the auricular points in the intervention was not explained in 46.7% of the studies. Besides, the term used to refer to auriculotherapy overlaps with six different terms, which makes it difficult to conduct a systematic review for auriculotherapy. In particular, there was no uniform terminology used within the nursing discipline. The use of standardized terminology can facilitate communication among nurses or with other health care providers and guide future studies through the synthesis of results [25]. Therefore, researchers should make an effort to unify terminology on auriculotherapy and establish the completeness, clarity, and transparency of the papers through detailed reporting that follow the guidelines.

Finally, multidisciplinary studies can generate higher impact on the science community by providing better evidence for intervention. A bibliometric analysis of 17,002 papers on various CAM therapies published during 1980∼2009 has shown that collaborative studies indicated higher citation impact than single discipline studies [26]. As presented in this study, the number of studies on auriculotherapy in other academic disciplines is also increasing. Therefore, nursing researchers should create opportunities for further improvement in auriculotherapy through a collaborative study based on a multidisciplinary approach.

This study provided an overview of research trends and intervention characteristics in auriculotherapy studies published in Korea. Nursing studies have been growing the body of evidence as well as improving quality in auriculotherapy during past 10 years. More rigorous design, and systematic report according to guidelines are becoming significantly important for healthcare providers as well as researchers. The results of this study call for further discussion to develop detailed nursing guidelines in auriculotherapy.

The authors declared no conflict of interest.