Introduction

In China, it is estimated that nine hundred million traditional Chinese Medicine consultations took place in 2009, of which acupuncture is a significant part of ref. 1. Often, related therapies, such as electro-acupuncture, auricular therapy, moxibustion, cupping, and transcutaneous electrical nerve stimulation (TENS) are also used in conjunction with acupuncture or on their own as a modality of treatment for various ailments and medical diseases. Traditional needle acupuncture has been gaining increasing popularity beyond China, as patients are becoming increasingly aware of and accepting of said acupuncture and its related modalities in the West. In the UK, approximately 4 million acupuncture sessions were offered to patients in 2009, with about two-third provided beyond the National Health Service2. In America, 3.1 million adults and 150,000 children used acupuncture in 20073, which increased approximately by 1 million since 20024. In 2003, 11% of Canadian adults sought help from complementary and alternative medicine (CAM), 2% of whom visited acupuncturists5.

In the UK, acupuncture and related therapies are most popular amongst patients with musculoskeletal pain and neurological conditions like headache and migraine2. Besides acupuncturists, it is also practiced by doctors, nurses, and physiotherapists with varying levels of training2. Although it is a common impression that acupuncture and related therapies are safe procedures, both minor and serious adverse events can occur during its use. Many publications have reported these adverse events but they are hard for clinicians to digest as they were written in inconsistent formats. The goal of this overview is to synthesize comprehensively existing systematic reviews on adverse events associated with acupuncture and related therapies, thus informing clinicians, acupuncturists, and patients alike on applying such treatments in a clinically mindful manner.

Results

Results on literature search and selection

Electronic database search identified 1,597 citations, with 387 duplicates that were excluded before the screening process. Among the remaining 1,210 records, 1,183 were excluded based on title and abstract screening, leaving 17 publications for full text assessments. All of the 17 were found to be eligible and were included in the present overview. See Fig. 1 for the flow diagram of literature search and selection.

Figure 1
figure 1

Flowchart of literature selection on systematic reviews of acupuncture related adverse events.

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Characteristics of included reviews

The 17 reviews were published between 1996 to 2015. The included reviews reported adverse events from a median of 43 primary studies (range, 9 to 167) and a median of 279 patients (range, 21 to 111,692). All 17 reviews were published in English. Seven (41.2%) reviews included only case reports, and the rest (10, 58.8%) included multiple study designs, including randomized or non-randomized clinical trials, cohort studies, case-control studies, cross-sectional studies, and case series. One review (5.9%) focused only on auricular acupuncture and related auricular therapies6, one (5.9%) focused only on electro-acupuncture7, six (35.3%) focused only on needle acupuncture8,9,10,11,12,13, three (17.6%) did not limit the type of acupuncture or related intervention that were included14,15,16, and the remaining six (35.3%) included two or more modalities, including needle acupuncture, electro-acupuncture, cupping, moxibustion, laser acupuncture, indwelling needles, dry needling, bee venom acupuncture, acupuncture point injection, and acupressure17,18,19,20,21,22. Four reviews (23.5%) included studies from China only7, 10, 17, 19, one (5.9%) included studies from the United States only8, one (5.9%) included studies from Norway only13, one (5.9%) included studies from Japan only12, and one (5.9%) included studies from the UK only11. The remaining reviews (9, 52.9%) included studies from two or more countries. See Table 1 for full details.

Table 1 Characteristics of included systematic reviews on acupuncture related adverse events.
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Methodological quality of included reviews

Fifteen (88.2%) reviews conducted a comprehensive literature search. No review provided an a priori design to their reviews via protocol publication. Thirteen (76.5%) review provided characteristics of their included studies. No review provided lists of both included and excluded studies. Eleven (64.7%) reviews reported the presence or absence of conflict of interests on the review itself. Only one (5.9%) review assessed the scientific quality of the included primary studies. The use of appropriate statistical methods and assessment on the likelihood of publication bias were not applicable as no meta-analysis was conducted amongst all included reviews. See Table 2 for full details.

Table 2 Methodological quality of included systematic reviews on acupuncture and its adverse events and/or complications.
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Adverse Events

Major results are narratively presented in this section and detailed information about the cases, including age and sex, reason for treatment, training background of practitioner, site of treatment, and follow-up time and outcome can be found in Table 3. A full list of results can be found in the Appendix 2.

Table 3 Most common adverse events and complications associated with acupuncture.
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Organ or tissue injuries (including complications from broken or remnant needles) associated with acupuncture

A median of 36 organ or tissue injuries were reported amongst 13 reviews7,8,9,10, 12, 13, 15,16,17,18,19,20, 22. A median of 4 deaths were reported across reviews, but four reviews did not report any data on outcomes8, 9, 12, 13. The most common organ or tissue injuries that occurred in patients included pneumothorax (8 reviews10, 12, 13, 15, 17,18,19, 22, median, 25.5, median number of deaths, 3), central nervous system or spinal cord injury (6 reviews7, 12, 13, 16,17,18, median, 13), subarachnoid or intracranial hemorrhage (3 reviews8, 10, 19, median, 35, median number of deaths, 2.5, with 1 review not providing outcome data19), and cardiac tamponade or heart injury (3 reviews7, 15, 20, median, 7, median number of deaths, 1). Respectively, one review reported each of the following as one of the most common organ or tissue injuries: pseudoaneurysm (7 cases)20, hematoma (44 cases)9, broken needle/needle fragment (4 cases)22, soft tissue injury (3 cases)8, and thumb deformity (12 cases)9. No deaths were reported for any of these complications. See Table 3 for full details.

Infections associated with acupuncture

A median of 17 infections were reported amongst 11 reviews6, 9, 10, 12,13,14, 16,17,18,19, 22. A median of 0.5 deaths was reported, but 5 reviews did not report any data on outcomes6, 9, 12,13,14. The most common infections that occurred in patients included hepatitis (3 reviews12, 13, 16, median, 94, 1 death in total), abscesses (4 reviews10, 12, 17, 22, median, 7), tetanus (3 reviews10, 17, 19, median, 6, median number of deaths, 3), auricular infections (3 reviews9, 13, 16, median, 9), septic arthritis (2 reviews9, 22, median, 4), local infections (2 reviews6, 19, median, 7.5), Mycobacterial infection (2 reviews9, 22, median, 244), Staphylococcal infection (1 review18, 29 cases). See Table 3 for full details.

Local adverse events or reactions associated with acupuncture

A median of 8.5 local adverse events or reactions were reported amongst 12 reviews6,7,8,9,10, 12, 13, 16,17,18,19, 22. No deaths were reported. The most common local adverse events or reactions that occurred in patients included contact dermatitis or local allergic reactions (9 reviews6, 9, 10, 12, 13, 16, 17, 19, 22, median, 4), argyria (4 reviews12, 13, 18, 22, median, 3), local bleeding (2 reviews8, 9, median, approximately 44), local pain or tenderness (2 reviews6, 10, median, approximately 71.5), local burns (4 reviews7, 16, 18, 19, median 1.5), and local bruising (1 review8, 1 case). See Table 3 for full details.

Other complications associated with acupuncture

A median of 21 other complications were reported amongst 11 reviews6, 7, 9, 10, 12, 13, 16,17,18,19, 22. No deaths were reported. The most common other complications that occurred in patients included dizziness or syncope (8 reviews6, 10, 12, 13, 16,17,18,19, median, 10.5), nausea and vomiting (2 reviews6, 16, median, approximately 11.5), and epilepsy (3 reviews, median, 2). Respectively, one review reported each of the following as one of the most common other complications: reduced bowel movements (2 cases)13, atrioventricular block (17 cases)7, factitial panniculitis (2 cases)22, aggravation of Bell’s palsy (13 cases)7, galactorrhea (2 cases)18, initial crying with fear and possible minor pain (approximately 62 cases)9, vasovagal reaction (13 cases)9, and aphonia (2 cases)10. See Table 3 for full details.

Discussion

This overview provided a comprehensive summary of all the adverse events and complications associated with acupuncture and related therapies that have been reported to date in published systematic reviews, with the majority coming from case reports, case series, and randomized controlled trials across 17 publications. The number of included primary studies in these publications ranged from 9 to 167. Amongst these primary studies, the number of included patients ranging from 21 to 111,692. In general, the results show that both minor and serious adverse events can occur from the use of acupuncture. Incidence rates, related confidence intervals (CIs), and p values could not be calculated because many adverse events came from case reports and many of the reviews did not include full details about the number of participants in their included studies. However, all the reviews have suggested that adverse events are rare and often minor.

Although serious complications were rare, they require significant attention as mortalities are associated with these adverse events. There was insufficient data to determine which body sites or whether patient predispositions were associated with these events, but it is clear that patients can be at great risk. Practitioners should pay ample attention to risk stratifying patients based on their medical history and other relevant characteristics. Other potential areas of improvement include enforcing stricter sterile needle practices, improving patient education about common and/or serious risks, and enhancing practitioner recognition of acute complications. Better communication should exist between physicians treating complications and the practitioner that administered the acupuncture, so that practitioners can become more cognizant of issues that can arise from their practice.

The methodological quality of the included reviews was mediocre. The majority of the included reviews conducted a comprehensive literature search. Most reviews also included the characteristics of their included studies and stated any conflicts of interest. However, no studies provided an a priori design, and only one study6 thoroughly assessed the scientific quality of included studies, which might be caused by lack of appropriate methodological quality assessment tools for case reports23. Regardless, the reviews provided a tantamount of information on the existence of adverse events in the literature across studies from around the world. A major limitation of the presented information was that no causality could be determined. In the reviews that commented on the scientific quality of included studies, concern was raised regarding the ability to ascertain that acupuncture resulted in the adverse outcome8, 10, 11, 14, 22. One review classified reported cases on a causality scale, and only a minority of adverse events were classified as certainly caused by acupuncture19. Future studies need to be more rigorous in their assessment of causality, and document their means of determining causality. Ideally, prospective cohort studies or randomized controlled trials should be reporting all the adverse events that occur during their investigations, as these provide the best evidence for causality. For rarer adverse events, case-control studies would be the ideal design. Another limitation is that a significant number of adverse events were not followed up. Although most complications were minor, practitioners and researchers should still follow up with the patient so that meaningful and definitive data can be derived. It is improper to assume that minor complications resolve spontaneously, or that major complications result in long-term implications. More attention needs to paid on the documentation and follow-up of all adverse events that occur during a study. Furthermore, a standardized template should be developed in the near future so that practitioners around the world can use it to track and report complications for research and clinical purposes.

Due to the diversity in study designs (e.g. case report, case series, case control studies, cohort studies, and clinical trials), populations, and data collection methods included in the identified systematic reviews, none of them conducted a meta-analysis to generate a pooled incidence rate with CI24. Although systematic reviews on adverse events are recommended to summarize evidence in a qualitative manner, a quantitative estimation of the upper limit of the 95% CI for the probability of the adverse events will help the clinicians to estimate what the worst-case scenario could be24. Future systematic reviews on this topic should use available statistical method25 to provide such a quantitative estimation. For primary studies, case control studies is the preferred method give the rare occurrence of adverse events.

Another concern raised by most reviews was the issue of underreporting10, 11, 13, 15, 16, 19,20,21. Often, only medically interesting findings are reported as many case reports are published by the physicians treating them16. Minor, less significant adverse events are often not published. Some reviews found that no adverse events were reported by acupuncturists12, raising the question of whether some practitioners are even aware of complications in their patients. Many journals restrict the type of publications that are accepted, and thus publication bias can also limit the number of adverse events reported20. This is a systemic issue, and regulatory bodies around the world need to create a convenient platform for which practitioners providing acupuncture and physicians treating complications can report known adverse events and the surrounding circumstances which can help with epidemiological and clinical research. In addition to providing a comprehensive summary, this overview serves as an important step towards furthering the knowledge, safety, and application of acupuncture. The overview may inform practitioners around the world about and modify the way they practice acupuncture, given that many acupuncturists may not be fully aware of the full breadth and depth of risk their treatments can pose. Usage of acupuncture is increasing worldwide, and more acupuncturists are being trained to match the demand. Thus, the need to pay careful attention towards the risks of acupuncture is becoming increasingly paramount as more patients become subject to it.

Methods

Inclusion criteria

Any systematic review (SR) that summarized adverse effects of acupuncture and related therapies, including electro-acupuncture, cupping, moxibustion, laser acupuncture, indwelling needles, dry needling, bee venom acupuncture, acupuncture point injection and acupressure, were considered eligible for this overview. To be included, the SR must have a primary objective of identifying adverse events instead of investigating its treatment efficacy or effectiveness. We had no restriction for the type of patients included, as long as they received acupuncture or related therapies for the management of any diseases or symptoms. We did not set any restriction on the control treatment as long as adverse effects of acupuncture were reported. However, SRs on adverse effects specifically caused by injected drugs through acupoint injections were excluded.

Literature search

MEDLINE and EMBASE were searched from their inception to December 2015. Published search filters related to SR26, 27 and adverse effects28 were used during the literature search, in addition to search keywords for acupuncture and related therapies. Details on search strategies as well as the retrieved results from the electronic databases could be found in Appendix 1.

Literature selection, data extraction and assessments of the methodological quality

Literature search was conducted by one researcher, and retrieved results were equally distributed to 4 pairs of trained research assistants. Each pair of assistants independently screened and evaluated the eligibility of citations that were assigned to them, and extracted data from the included reviews using a standardized, piloted template. The template was designed according to the requirement of the PRISMA harm checklist29. Disagreements were resolved via discussion and consensus within each pair. A senior researcher was consulted when disagreement was unresolvable.

Methodological quality of included SRs were evaluated with the validated Methodological Quality of Systematic Reviews (AMSTAR)30 instrument by two researchers independently. It includes 11 items, with each item being assessed as yes, no, cannot answer, or not applicable based on information provided by the SRs. Disagreements between assessors were discussed to reach consensus. A third reviewer was consulted if necessary.

Data synthesis

Adverse effects of acupuncture and related therapies and their outcomes were narratively reported according to each adverse event. Protocol of this overview has been registered in PROSPERO (http://www.crd.york.ac.uk/PROSPERO/printPDF.php?RecordID=43943&UserID=6569).