Introduction

Migraine is a common primary headache disorder characterized by recurrent headaches associated with nausea, vomiting, photophobia and phonophobia.1 Currently, the number of migraine sufferers in the world is 1.1 billion, migraine is the second most disabling disease worldwide.2,3 The male-to-female prevalence ratio is approximately 1:3.4 Compared to 1990, there is a significant increase in annual incidence and age-standardized point prevalence compared to 1990.3 Migraine management is based on oral medications. Migraines have an increased risk of comorbidities than individuals without migraine,5 but comorbidities can limit their medication.6 When acute treatments are ineffective, there is an increased risk of conversion to chronic migraine.7 Chronic migraine severely impacts a patient’s quality of life and socioeconomic functioning.8

Acupuncture is a component of traditional Chinese medicine consisting in thin needles inserted through the skin at specific points to cure diseases or relieve pain. A recent meta-analysis showed that acupuncture has advantages in improving intracranial blood circulation, reducing the frequency of migraine attacks, and lowering pain scores. Whether compared with sham acupuncture or traditional medicine, acupuncture has outstanding advantages and fewer adverse reactions.9

Bibliometrics is a set of interdisciplinary methods to quantitatively analyze scientific literature.10,11 Although the role of citation counts is controversial, it is also increasingly important to identify the most influential studies in a specific field.12 Citation count is widely used in obstetrics and gynecology,13 brain surgery,14 neuroscience,15,16 imaging,17 gastroenterology18 and oncology.19,20 VOSviewer21 and CiteSpace22 are two commonly used programs for analyzing and measuring scientific literature. To date, no bibliometric analysis has been performed on the 100 most highly cited publications on acupuncture for migraine. This study visually analyzes the 100 most highly cited publications on acupuncture for migraine. We also provided a brief historical overview and landmark studies investigating acupuncture for migraine.

Methods Search Strategy

The Science Citation Index Expanded (SCI-EXPANDED) of Web of Science Core Collection (WoSCC) was retrospectively searched from inception to June 24, 2022. The search strategy was as follows: (TS = (acupuncture*) OR (electroacupuncture) OR (moxibustion) OR (acupoint*)) AND (TS = (migraine*)). Only original studies or review articles published in English were included.

Data Collection

The 100 most highly cited publications on acupuncture for migraine were ranked in descending order of citations. Two researchers reviewed the titles and abstracts, read the full texts when necessary and sought the help of a third researcher when disagreement arose.

Analysis Tools

CiteSpace (6.1.R2) and VOSviewer were used to perform the bibliometric analysis of retrieved articles. CiteSpace parameters were set as follows: Time Slicing from 1984 JAN to 2020 DEC (Years Per Slice = 1), Node Types selecting (Author or Institution or Country or Keyword or Reference), Selection Criteria selecting g-index (k = 25), Pruning selecting (Pathfinder, Pruning Sliced Networks and Pruning Merged Network).

Statistical analysis was performed using IBM SPSS Statistic version 26.0. The Kendall’s rank correlation was employed to test for correlations between publication date and citations.23

Results Annual Trends of Publications

The 100 most highly cited publications on acupuncture for migraine were cited 6142 times with an h-index of 44 (Table 1). The highest number of cited articles was 416. The oldest study was published in 1984 (Figure 1A). While the year with the highest citation frequency was 2020 (n=664), 2021 and 2019 were ranked second and third (Figure 1B). Most of the historical studies were published in 2017. The most frequently cited study (n=416) was Acupuncture for patients with migraine: a randomized controlled trial by Linde et al. The study was published in the 2005 by Journal of the American Medical Association (JAMA). There is a significant correlation between the current citation (measured as the number of citations in 2021) of an article and its publication date (r=0.357, p=0.000<0.01, Figure 2A). Further, a significant negative trend towards an increased overall citation was observed (r=−0.223, p=0.001<0.01, Figure 2B). Among the included studies, 83% were original studies and 17% were review articles (Table 2). The research directions belonged to 13 disciplines. The most common disciplines were neuroscience and neurology, internal medicine and complementary medicine.

Table 1 The 100 Most Highly Cited Publications on Acupuncture for Migraine

Table 2 Document Types and Research Areas for the 100 Most Highly Cited Publications on Acupuncture for Migraine

Figure 1 (A) Annual trends of the 100 most highly cited publications on acupuncture for migraine. (B) The top 3 years with the highest citation frequency.

Figure 2 Association of (A) current (2021= last full year) citation rate and (B) overall citations with the year of publication.

Author Analysis

A total of 335 authors contributed to the 100 most highly cited publications on acupuncture for migraine. According to the Price Law formula (), authors with more than 2.90 publications were considered main authors. There were 34 main authors and 19 authors with at least five publications (Table 3). A total of 15 papers were published by Linde K, who was the largest contributor with 1914 cumulative citations. About 12 and 10 papers were published by Liang FR and Allais G, respectively. Figure 3 shows the co-linear mapping between authors. The authors were roughly divided into three groups: Liang FR, Linde K and Allais G. The authors on Liang FR’s team work closely together. The Linde K team has the largest number of members, and there is a collaboration between the Allais G and Linde K teams.

Table 3 Main Authors with More Than Five Publications of the 100 Most Highly Cited Publications on Acupuncture for Migraine

Figure 3 The author-collaboration network of the 100 most highly cited publications on acupuncture for migraine.

Country and Institution Analysis

According to the results of the analysis, 20 countries were involved in studies on acupuncture for migraine (Figure 4). The most published studies came from the United States (n=36), followed by China (n=27) and Germany (n=26) (Table 4).

Table 4 Countries of the 100 Most Highly Cited Publications on Acupuncture for Migraine

Figure 4 The country-collaboration network of the 100 most highly cited publications on acupuncture for migraine. The node radius represents the number of published documents, and the larger the number of published documents, the larger the radius. The color is related to the year of publication, and the darker the color, the larger the year. A node with a purple outer ring is a critical node, meaning that the centrality of the mediation is greater than 0.1.

A total of 212 institutions were involved in publishing at least one study on acupuncture for migraine (Figure 5). A total of 19 institutions published more than three papers, with the top five publishers being the Technical University of Munich (n = 15), the Chengdu University of Traditional Chinese Medicine (n = 13), Charité University Hospital of Berlin (n = 13), the Memorial Sloan Kettering Cancer Center (n = 9) and the University Hospital of Zurich (n = 9).

Figure 5 The organization cooperation network of the 100 most highly cited publications on acupuncture for migraine.

Journal Analysis

The 100 most highly cited publications on acupuncture for migraine were published in 50 journals (Table 5). Headache published 13 papers and was the most contributing journal. Based on the 2021 Impact Factor (IF), 11 journals with an IF more than 10 published 16 highly cited publications with 1789 citations, accounting for 29.13% of the total citations. Among them, BMJ-British Medical Journal published the largest number of papers (n=3), followed by Canadian Medical Association Journal (n=2), Cochrane Database of Systematic Reviews (n=2), and Journal of Internal Medicine (n=2). Encouragingly, one article with 416 citations was published in the JAMA (IF=157.335, Q1).

Table 5 Journals of the 100 Most Highly Cited Publications on Acupuncture for Migraine

Keyword Analysis

We found 140 keywords (Figure 6). The most popular keywords were “acupuncture”, “migraine”, “headache”, “randomized controlled trial”, “pain”, “complementary medicine”, “prophylaxis”, “alternative medicine”, “meta-analysis” and “treatment”. The average S = 0.8431 > 0.7 indicated that the ten clusters were reliable (Figure 7).

Figure 6 Keyword co-occurrence network map of the 100 most highly cited publications on acupuncture for migraine.

Figure 7 Keyword co-occurrence cluster map of the 100 most highly cited publications on acupuncture for migraine.

Analysis of Co-Cited Literature

The co-cited literatures were divided into 14 clusters (Figure 8A). In the timeline view, clustering #5 (fMRI-based neural marker) is the main focus of recent studies (Figure 8B). The node represents references, the abscissa represents the year of initial reference, and the ordinate represents cluster. Node and font size are positively correlated with reference frequency. The most cited article was published by Linde K in 2005.

Figure 8 (A) Cluster map of co-cited reference based on label clusters with title terms. (B) Timeline view of co-cited references of the 100 most highly cited publications on acupuncture for migraine.

Discussion Basic Information Analysis

We analyzed the year of publication, frequency of citations, and disciplinary distribution of these publications. Among the 100 most highly cited publications, the earliest heavily cited study was published in 1984, and after a decade of silence, at least 1 highly cited paper was consistently published starting in 1994 (excluding 1996), reaching its highest level in 2017 (n=10). A publication by Linde K published in 2005 had the highest citation frequency (n=416). Research in the field of acupuncture for migraine has been frequently cited in the last three years, indicating a continued increase in interest in the field. This study covered a wide range of disciplines- neurology,32 general medicine,29 complementary medicine,106 anesthesiology25 and pediatrics.34 These results suggest that the analgesic effects of acupuncture are of interest to multiple disciplines, and that acupuncture is used not only in adult migraine but also plays an active therapeutic role in childhood migraine.

A total of 50 journals were involved in publishing the 100 most cited publications. Sixteen papers were published in journals with an IF greater than 10, and 54 papers were published in journals with an IF greater than 5. The two most published journals were Headache (n = 13) and Cephalalgia (n = 8), both of which are leading journals in clinical neurology. In addition, several articles were published in top journals such as JAMA (IF = 157.355), BMJ-British Medical Journal (IF = 96.2) and Lancet Neurology (IF = 59.935). Journals with high partition and high IF have a high academic impact and high-quality papers are usually published in such journals. In the present study, most of the journals belonged to the JCI Quartile Q1 (n=32), and these results suggest that the field of acupuncture for migraine has attracted wide attention from researchers and the quality of publications is excellent.

We analyzed the distribution of authors, countries/regions, and institutions for these publications. A total of 335 authors were involved in this study. The top three most prolific authors were Linde K, Liang FR and Allais g. Linde K was one of the most influential authors, publishing papers with 31.16% of the total citations. The most cited publications also came from Linde K. A total of 20 countries and 212 institutions were involved in the study, and the United States was found to have the highest number of publications, followed by China and Germany. Research institutions from the US, China, and Germany published more than 73% of the 100 highly cited publications Among the top five institutions publishing the most articles, Germany and the US each had two institutions, and only one institution from China was selected. It is noteworthy that since the first highly cited paper from China was published in the SCI-E database in 2008, Chinese scholars have published 22 articles so far. This represents 32.35% of the top 100 cited articles (n = 68) and 948 citations, accounting for 28.15% of the total citations after 2008 (n = 3367). China is gradually becoming the most influential country in the field of acupuncture for migraine treatment.

Research Hotspots

By removing the subject terms (acupuncture and migraine) and the disciplinary terms (complementary medicine and alternative medicine), the main keywords were “headache”, “randomized controlled trial”, “migraine”, “pain”, “prophylaxis”, “chronic pain”, “meta-analysis”, “systematic review” and “treatment”.

Clinical Studies

The 100 most highly cited studies investigated different types of migraine, such as migraine without aura,43 chronic migraine49 or menstrually related migraine.91 Regarding the acupuncture techniques, the conventional acupuncture, ear acupuncture, laser acupuncture and electroacupuncture achieved good results. Romoli et al121 published a case report documenting the ability of ear acupuncture to reduce pain in migraine patients until 24 hours. A randomized trial confirmed the efficacy of ear acupuncture for migraine.79 Gottschling et al59 investigated the efficacy of laser acupuncture vs placebo for the treatment of childhood headache. The results showed a significant reduction in the average number of headaches per month in children treated with laser acupuncture. Other studies investigated the optimal selection of acupuncture points. In 37 patients with frequent headaches, most of the subjects were found to have the “liver stagnation and qi stagnation” syndrome, with the optimal acupuncture points being Tai Chong (LR3), He Gu (LI4) and Bai Hui (DU20).74 Interestingly, the clinical efficacy of several combinations of acupuncture points differed.64

Systematic Reviews and Meta-Analyses

Systematic reviews and meta-analyses played a major role in this study. The results of the most cited controlled trials showed no difference between acupuncture and sham acupuncture in migraine patients.24 However, newer systematic reviews with more high-quality studies suggested a beneficial effect of acupuncture for migraine. Two systematic reviews published by Linde et al28,33 demonstrated that acupuncture is comparable to, and perhaps even more effective than, prophylactic medications, but long-term studies are lacking. In addition, a few systematic reviews focused on chronic pain. A meta-analysis of high-quality trials showed that about 90% of the positive effects of acupuncture on chronic pain, including headache and migraine, lasted up to 12 months.46 The beneficial effects and long-term efficacy of acupuncture are supported by scientific evidence so far. Furthermore, acupuncture has been listed in several guidelines for migraine treatment.65,77,87,110

Future Trends

The field of acupuncture for migraine has progressed since 2008. Increasing cooperation between countries has contributed to further developments. Since 2008, China ranks first among all countries in terms of number of publications and citations. China is gradually becoming one of the most influential countries investigating acupuncture for migraine. Despite the conventional use of acupuncture as a treatment, research in the field has not been limited to efficacy. The 100 most highly cited publications covered studies on the pathogenesis of migraine, acupoints specificity and the mechanisms of acupuncture. The continued interest of researchers has contributed to the diversity and innovation in this area.

The clustering #5 is the most relevant topic in the 100 most highly cited publications. Only two studies focused on biomarkers, one of them was conducted in animals.109 In recent years, there has been an increasing number of studies using neuroimaging. Liang FR as the most represented corresponding authors previously combined neuroimaging with acupuncture. Li et al98 suggested that the resting state functional connectivity (rs-fc) of right frontoparietal network (rFPN) was abnormal in brain regions of migraine patients compared to healthy individuals. The rs-fc of rFPN improved after acupuncture treatment and the improvement was positively correlated with headache relief. Different acupuncture points induced different levels of cerebral glucose metabolism in pain-related brain regions.64 The changes in brain glucose metabolism were correlated with acupuncture points by PET-CT.93 Using machine learning and fMRI, some researchers identified a neural marker to distinguish migraine patients without aura from healthy individuals.88 These neuroimaging-related studies exploring the pathogenesis of migraine provided new ideas on the mechanisms of central analgesia in acupuncture.

Limitations

This study is affected by some limitations. First, the subject of this study concerns the 100 most highly cited publications on acupuncture for migraine. The recent articles with high citation potential or the latest finding may not be included. Second, acupuncture is widely used in China, Japan, and Korea. Publications using non-English languages were not included because we focused solely on English-language studies. Third, this study only searched the WOS database, possibly missing some highly cited papers.

Conclusion

This is the first bibliometric analysis of the 100 most highly cited papers on acupuncture for migraine. The USA, China and Germany are the most influential countries. The Technical University of Munich is the most prestigious institution in the field, while Headache is the leading journal. Clinical research is the focus of this field. Future research will focus on the mechanism exploration of acupuncture for migraine, and pairing these treatments with neuroimaging will undoubtedly become popular.

Acknowledgment

We thank all the authors of the original studies included in this analysis.

Author Contributions

XS designed the study. XS and JQW performed the search and analyzed the data. XS, JQW, LB and WZ contributed to the literature review. All authors contributed to the article and approved the submitted version. All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Funding

There is no funding to report.

Disclosure

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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