Analysis of the Most-Cited Systematic Review or Meta-Analysis in Acupuncture Research

Objectives The aim of the current study was to analyze the 100 most-cited systematic reviews or meta-analyses in the field of acupuncture research. Methods The Web of Science Core Collection was used to retrieve lists of 100 most-cited systematic reviews or meta-analyses in the field of acupuncture research. Two authors screened literature, extracted data, and analyzed the results. Results The citation number of the 100 most-cited systematic reviews or meta-analyses varied from 65 to 577; they were published between 1989 and 2018. Fourteen authors published more than 1 study as the corresponding author and 10 authors published more than 1 study as the first author. In terms of the corresponding authors, Edzard Ernst and Linde Klaus published the most systematic reviews/meta-analyses (n = 7). The USA published most of the systematic reviews or meta-analyses (n = 24), followed by England (n = 23) and China (n = 14). Most institutions with more than 1 study were from England (4/13). The institutions with the largest numbers of most-cited systematic reviews or meta-analyses were the Technical University of Munich in Germany, the University of Maryland School of Medicine in the USA (n = 8), the Universities of Exeter and Plymouth in England (n = 6), and the University of Exeter in England (n = 6). The journal with the largest number of most-cited systematic reviews or meta-analyses was the Cochrane Database of Systematic Reviews (n = 20), followed by Pain (n = 6). Conclusion Our study reveals that the 100 most-cited systematic reviews or meta-analyses in the acupuncture research field are mostly from high impact factor journals and developed countries. It will help researchers follow research hot spots, broaden their research scope, expand their academic horizons, and explore new research ideas, thereby improving the quality of acupuncture research.


Introduction
Acupuncture is an important therapy in the traditional medicine of China and has been practiced for thousands of years [1]. It is defined as the insertion of one or several needles into the skin at particular sites for therapeutic purposes [1,2]. e acupuncture research has shown impressive development during the past decade, and published articles have reflected its evolution [3,4]. e Science Citation Index was initiated at the Institute for Scientific Information by Eugene Garfield, which is now owned by Clarivate Analytics [5]. It maintains a systematic ongoing measurement of citation counts for scientific journals and articles. e citation number of an article by other articles is widely considered as an important parameter to measure its relevance in the field of knowledge [6,7]. Citation analysis can be used to identify studies that have influenced a given field, and a highly cited paper is usually seen as a landmark in any medical discipline, and it may influence further research and clinical practice [8]. In addition, the top-cited articles are often written by leading experts who can offer insight into future directions of the discipline and indicate the growth of particular fields [9].
Several recent studies have identified and analyzed citation classics and most-cited articles in various medical fields including gastric diseases [8], antibiotics [10], obstetrics and gynecology [7], and attention-deficit/hyperactivity disorder [11]. However, to the best of our knowledge, no comprehensive studies reported the most-cited systematic reviews or meta-analyses in acupuncture research, especially using the Web of Science database.
us, we performed the current study to identify the 100 most-cited systematic reviews or meta-analyses published in journals in the field of acupuncture research.

Search Strategy.
e Web of Science Core Collection was searched for the 100 most-cited systematic reviews/metaanalyses using the following search terms: (Acupuncture [Topic] OR Acupuncture [Title]) AND (systematic review [Topic] OR meta-analysis [Topic] OR systematic review [Title] OR meta-analysis [Title]). e last search was performed on May 5, 2021. e results were screened and ordered by the total number of citations, and the 100 mostcited systematic reviews or meta-analyses were included for data analysis.

Data Collection and Analysis.
e 100 most-cited systematic reviews or meta-analyses were exported into one electronic datasheet and analyzed. Data were inserted into an Excel database (Excel 2010, Microsoft), and a descriptive statistical analysis was performed by Excel software. Structural visualization and analysis of the 100 most-cited studies were performed using VOSviewer 1.6.66 (https://www.vosviewer.com/, Leiden University Centre for Science and Technology Studies). For each study, the characteristics of the study such as the number of citations, ranking, authorship, title, year of publication, published journal, publication type, and topic categories were assessed by two authors. If the authors of an article had more than one affiliation, the department, institution, and country of origin were defined by the first affiliation of the first author.

Results
e search results included more than 1,500 systematic reviews or meta-analyses. After screening the titles and abstracts, the 100 most-cited systematic reviews or metaanalyses were selected for data analysis. Table 1 shows the 100 most-cited systematic reviews or meta-analyses; they are ranked according to the number of citations. e total citation numbers of all 100 most-cited systematic reviews or meta-analyses were 13,459, varying from 65 to 577. Fifteen systematic reviews or meta-analyses had been cited more than 200 times. e most-cited systematic review/metaanalysis was Acupuncture, which was written by Vickers et al. in Arch. Intern. Med. published in 2012 with the citation number of 577 [12]. e second systematic review/ meta-analysis was "Do certain countries produce only positive results? A systematic review of controlled trials" written by Vickers et al. published in Control Clin Trials in 1998 with the citation number of 425 [13]. e third systematic review/meta-analysis was "Is acupuncture effective for the treatment of chronic pain? A systematic review" written by Ezzo et al. published in Pain in 2000 with the citation number of 293 [14].
As to the authors, the results showed that there were 14 corresponding authors who published more than one study and 10 authors who published more than one study as first authors. In terms of the corresponding authors, Edzard Ernst and Linde Klaus published the most studies (n � 7).
e author with most studies as the first author was Edzard Ernst who published 6 studies. Table 2 summarised the characteristics of the authors.
As shown in Table 3, the 100 most-cited systematic reviews or meta-analyses were from 16 countries, respectively. e USA ranked first with 24 studies, followed by England (n � 23) and China (n � 14). When considering the average citation, the average citations of the Chinese authors were less than authors from other countries. Table 4 shows institutions that published at least two most-cited studies. ere were four institutions from England that published at least two most-cited studies, including the Universities of Exeter and Plymouth, the University of Exeter, the University of York, and Research Council for Complementary Medicine. As for the number of most-cited studies, the Technical University of Munich in Germany and the University of Maryland School of Medicine in the USA all ranked the first with eight studies; the Universities of Exeter and Plymouth in England ranked the second with seven studies. Table 5 shows the published year of the 100 most-cited systematic reviews or meta-analyses. Most of these studies were published in 2009 (n � 9) and 2010 (n � 9), and 8 studies were published in 2005, 2008, and 2013. e 100 most-cited systematic reviews or meta-analyses were published in 50 journals (Table 6). Two systematic reviews or meta-analyses were from stroke and were cited with an average of 133 times, which was in the moderate level. Among the 50 journals, impact factors (2020) of 5 journals were higher than 10, including Annals of Internal Medicine, British Journal of Sports Medicine, British Medical Journal, Journal of Clinical Oncology, and JAMA Internal Medicine. e cocitation of the 100 top-cited studies is shown in Figure 1. e most frequent cocited study was about quantifying heterogeneity in a meta-analysis (n � 31) published by Controlled Clinical Trials in 1996. e most frequent cocitied source was Pain (n � 280). Edzard Ernst from the University of Exeter in England was the most frequent cocitied author (n � 70).  Evidence-Based Complementary and Alternative Medicine 3     Osteoarthritis 68

Discussion
Acupuncture is undoubtedly valuable in Chinese traditional medicine. It is effective, especially in reducing chronic pain, such as cervical spondylosis and the management of low back pain [15][16][17]. In the field of acupuncture research, citation of studies varied. e most-cited studies ranked the highest position and could show research ability and development in different countries and institutions. us, analyzing the most-cited studies would help future studies. e numbers of citations of the 100 most-cited systematic reviews or meta-analyses were considerable. e data indicated that the researchers in the medical field give huge attention to acupuncture. Our results showed the top researches of acupuncture, investigating the distribution of authors, countries, institutions, year, and journals. e study showed that authors from the USA published most studies among the 100 most-cited studies. Although China is the birth land of acupuncture, the number of Chinese studies was only 14. Traditional Chinese clinicians might always focus on the clinical practice, ignoring the research, especially the study using modern scientific methods [18]. On the contrary, western researchers were proficient in research methods. So when they develop great interests in this field, they could perform studies with high quality. e institutions revealed that researchers in famous research-based universities or hospitals made huge efforts to investigate the principle and effectiveness of acupuncture, such as Technische Universität München, Harvard University, Massachusetts General Hospital, and the University of Maryland School of Medicine. Acupuncture was the traditional therapeutic method with large varieties of clinical practice, especially in China and other East Asian countries, which suggest that more attention should be paid to China in international journals.
In terms of journals, the number of systematic reviews or meta-analyses from the Cochrane Database of Systematic Reviews was the largest (n � 20) because this journal is dedicated to publishing systematic reviews. Besides, some highly influential journals, such as Annals of Internal Medicine, BMJ, and Journal of Clinical Oncology, also published some studies in this field. It is undoubted that papers published in highly influential journals would be cited more because of the great reputation of these journals; thus, we should publish more studies in highly influential journals.    In terms of the cocitation of the 100 most-cited studies, the results indicated that the most-cited studies were published in Pain; this might be related to the limitation of understanding on acupuncture by foreign researchers. Hence, it suggested that editors and authors should choose other interesting research topics of studies in the future.
It should be noted that Chinese researchers contributed 14 papers, and some Chinese authors were really outstanding. Jian-Ping Liu from Beijing University of Chinese Medicine published 1 study in PLoS One [19] and Journal of Alternative and Complementary Medicine [20]. Lee     published 1 study in Archives of Physical Medicine and Rehabilitation [24]. It should be noted that acupuncture was used most widely in China; due to language constraints, some excellent Chinese studies might not be cited, which might bias the conclusion of this study. e strengthening of exchanges and cooperation with international institutions and institutions had been identified as a priority in the acupuncture field. Hence, the acupuncture researchers should pay attention to the research in high-impact institutions and published high-impact researches in a timely manner, in order to promote interinstitutional cooperation and exchanges. ere were some limitations of our study. Our electronic search was performed in the Web of Science Core Collection. As a result, the bias of searching cannot be avoided [25]. In addition, a number of studies conducted by Chinese researchers were published in Chinese journals and have not been included in the current study, so the results should be explained with caution.
In conclusion, our study revealed that the 100 most-cited systematic reviews or meta-analyses in the acupuncture research field are mostly from high impact factors journals and are mostly from western counties. It will help researchers follow research hot spots, broaden their research scope, expand their academic horizons, and explore new research ideas, thereby improving the quality of acupuncture research.

Data Availability
e original data used to support the findings of this study are included within the article. Disclosure e funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Conflicts of Interest
e authors declare that they have no conflicts of interest.

Authors' Contributions
e corresponding author attests that all listed authors meet authorship criteria. Yonggang Zhang, Ning Li, and Nian Li provided ideas and designed the manuscript. Ying He and