Efficacy of Acupuncture in the Treatment of Essential Hypertension: An Overview of Systematic Reviews and Meta-Analyses

Abstract

Background: Acupuncture is widely used in the clinical treatment of essential hypertension(EH). To summarize current systematic reviews of acupuncture for EH, assess methodological bias and the quality of evidence.

Methods: Two researchers searched and extracted 7 databases for systematic reviews (SRs)/meta-analyses (MAs),and independently assessed the methodological quality, risk of bias, reporting quality, and quality of evidence of SRs/MAs included in randomised controlled trials (RCTs).Tools used included the Assessment of Multiple Systematic Reviews 2 (AMSTAR-2), the Risk of Bias in Systematic (ROBIS) scale, the list of Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA), and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system.

Results: This overview included 14 SRs/MAs that use quantitative calculations to comprehensively assess the various effects of acupuncture in essential hypertension interventions.The methodological quality, reporting quality, risk of bias, and quality of evidence for outcome measures of SRs/MAs were all unsatisfactory. According to the results of the AMSTAR-2 assessment, all SRs/MAs were of low and very low quality. According to the results of the ROBIS evaluation, a few SRs/MAs were assessed as low risk of bias.According to the results of the PRISMA checklist assessment, SRs/MAs that were not fully reported on the checklist accounted for the majority. According to the GRADE system, 86 outcomes were assessed under different interventions in SRs/MAs, and 2 were rated as moderate-quality evidence, 23 as low-quality evidence, and 61 as very low-quality evidence.Limitations of the included SRs/MAs included the lack of necessary items, such as not being registered in the protocol, not providing a list of excluded studies, and not analyzing and addressing the risk of bias that existed,etc.

Conclusion: Currently, acupuncture may be an effective and safe treatment for EH, but the quality of evidence is low, and caution should be exercised when applying this evidence in clinical practice.

1. Introduction

Essential hypertension (EH) is a common clinical disease caused by multiple factors such as heredity and environment. The main clinical manifestation is elevated arterial pressure in the systemic circulation, which can cause serious damage to multiple organs such as blood vessels, heart, brain, kidney, and eyes[1]. There is a strong, independent linear association between blood pressure and cardiovascular disease risk. Hypertension is an independent risk factor for cardiovascular disease[2], and its concurrent cardiovascular and cerebrovascular diseases not only cause disability and high mortality, but also consume medical and social resources, causing a heavy burden on families and the country[3]. With the development of society and the increase of life and work pressure, the incidence of hypertension is increasing year by year, and it is getting younger and younger. The burden of cardiovascular disease is heavy in my country, and effective control of hypertension is the top priority to reduce the burden of cardiovascular and cerebrovascular disease[4]. Usually, the conventional treatment of EH is mainly western medicine. Initial use of a single antihypertensive drug, followed by dose titration, sequential addition of other drugs to achieve antihypertensive goals[5],however, problems such as adverse reactions caused by long-term medication, limitations of drug tolerance and medical expenses have attracted more and more attention of patients. Therefore, it is imminent to find a treatment method that can effectively lower blood pressure, reduce adverse reactions, and effectively control complications[6].

Therefore, more and more scholars are exploring safer EH treatment methods. At present, some scholars have applied acupuncture with the characteristics of traditional Chinese medicine(TCM) to the treatment of EH. Many clinical studies[7–21] have shown that acupuncture can effectively control blood pressure: acupuncture may regulate the central nervous system[7–9] and the renin-angiotensin-aldosterone system (RAAS)[10–12], balance the imbalanced immune system[13–15], and improve the state of vascular structure[16–18], anti-oxidative stress[19–21]. Therefore, it is believed that acupuncture may be a safer and more effective antihypertensive therapy.

In recent years, evidence-based medicine has been deeply integrated with TCM clinical research, especially acupuncture clinical research. From the perspective of evidence-based clinical practice, systematic reviews(SRs) should be the best evidence to guide clinical practice. Through preliminary searches, the team found that there have been multiple SRs showing that acupuncture therapy has a certain effect on EH, but the methodological quality of these SRs is unclear, and the quality of the evidence provided is not clearly, therefore, our study aims to critically evaluate the quality of acupuncture in the treatment of EH through a comprehensive overview to provide clinical ideas and evidence support(The overview of SRs/MAs is a new way to comprehensively evaluate the methodological quality and quality certainty of multiple SRs/MAs.).

2. Materials And Methods

The methodology of this study follows the Cochrane Handbook, and the report of this overview is in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 checklist [22]. This overview has been registered with the PROSPERO website((Registration number:PROSPERO CRD42022361514).

2.1 Inclusion and Exclusion Criteria.

The criteria for inclusion of SRs/MAs in this overview are as follows:(1) SRs/MAs based on randomized clinical trials(RCTs), the language is limited to Chinese and English;(2) A definite diagnosis of EH, regardless of type, gender, age, and course of disease;(3) Interventions in the treatment group included one of the three methods of simple acupuncture, electro-acupuncture, and warm acupuncture or combined with the relevant treatment recommended by the guidelines (including lifestyle regulation, conventional antihypertensive drugs(CAD)),the control group was a guideline-recommended treatment regimen or a placebo sham acupuncture;(4) The main outcome indicators were the effective rate of blood pressure reduction, the improvement of systolic blood pressure(SBP) and diastolic blood pressure(DBP), the change of blood pressure before and after treatment, and adverse reactions.

The exclusion criteria are as follows: (1) duplicate publications, animal studies, narrative reviews, reviews,research protocols,and network meta-analysis; (2) literatures with incomplete data or unable to obtain the original text; (3) the subjects of the study were EH combined other illnesses.

2.2 Search Strategy.

Computer searched PubMed, Cochrane Library, Embase, Web of science, the Chinese National Knowledge Infrastructure(CNKI), Chinese Biological Medicine Database(CBM), and Wanfang Database, and the search period is from the establishment of the database to September 2022, hand-searched and traced references to supplement relevant literature.The search uses a combination of subject words and free words.Key search terms were derived from MeSH and included search terms such as: “Acupuncture”,“Essential hypertension”,“Systematic review” OR “meta-analysis”. The search strategies used in PubMed are shown in Table 1. Adjust to the specific needs of each database. In addition, we searched conference proceedings and dissertations to identify relevant grey literature.

2.3 Literature Screening and Data Extraction.

Two researchers (MX-F and XQ-W) independently screened and extracted the literature, and cross-checked them. If there was any disagreement, they were discussed and negotiated or the third expert (GH-D) decided. The extracted literature information included: authors, publication year, nationality, sample size, intervention measures, quality assessment tools and main conclusions.

2.4 Quality Assessment.

Two researchers (MX-F and XQ-W) independently assessed the methodological and evidence quality of the included SRs/MAs, Any discrepancies were resolved by consensus or adjudication by a third author (GH-D).

2.4.1 Methodological Quality Assessment.

The methodological quality of the included SRs/MAs was evaluated using the Assessment System for Evaluating Methodological Quality 2(AMSTAR-2)[23]. The AMSTAR-2 scale contains 16 items that can be answered with a "yes", "partially yes" or "no". According to the evaluation criteria, it can be rated "high", "mederate", "low" and "very low", and 7 out of 16 items in the tool (2, 4, 7, 9, 11, 13 and 15) are critical items.

2.4.2 Risk of Bias Assessment.

The bias level of each SRs/MAs included was independently assessed using Risk of Bias in Systematic Review (ROBIS)[24] tool. ROBIS is useful for assessing the extent of bias in four domains: (1) eligibility criteria for each study; (2) the identification and selection of studies; (3) data collection and study appraisal; and (4) overall synthesis and major findings. Within each domain, specific questions were used to determine the risk of bias, which was rated as ‘‘low,” ‘‘high,” or ‘‘unclear.”

2.4.3 Report Quality Assessment.

The quality of each SR/MA report for the included SRs/MAs was assessed by the PRISMA 2020[22] checklist, and each of the 27 items included in PRISMA 2020 was scored as “yes”, “partially yes” or "no".

2.4.4 Evidence Quality Assessment.

The Grading of Recommendations Assessment, Development, and Evaluation (GRADE)[25] system was adopted to evaluate the quality of evidence of included SRs/MAs outcome indicators.Since the initial quality of evidence for RCTs is high, the quality of evidence for the outcomes of the study was evaluated based on downgrading factors such as limitations,inconsistencies, indirectness, imprecision, and publication bias of the study. According to the downgrade level, they were rated as "high", "mederate", "low" and "very low".

3. Results

3.1 Literature Search and Screening Results.

A total of 273 related literatures were retrieved, and after layer-by-layer screening, 14 [26-39] literatures were finally included. The specific screening process is shown in Figure 1.

3.2 The Basic Characteristics of the Included Literature.

Among the 14 SRs/MAs included, 5[35-39] SRs/MAs were in English, 9[26-34] SRs/MAs were in Chinese, 13 SRs/MAs were studied in China, and 1[34] SR/MA was studied in South Korea, the publication year was 2009-2022, and the number of RCTs studies was 4-53. In terms of quality assessment of included RCTs, 8[28-30,32,34,37-39] SRs/MAs were assessed by the Cochrane risk of bias tool, and 5[26,27,31,33,36] SRs/MAs were assessed by the Jadad scale was used for evaluation, and 1[35] SR/MA used the Oxford scale. The intervention measures in the treatment group were one of the three methods of simple acupuncture, electro-acupuncture, and warm acupuncture or combined with the relevant treatment recommended by the guidelines (including lifestyle regulation, CAD),the control group was the relevant treatment methods recommended by the guidelines or placebo sham acupuncture.See Table 2 for specific information.

3.3 Results on SRs/MAs Quality Assessment.

3.3.1 Results of the Methodological Quality.

The quality of the included SRs/MAs was assessed by AMSTAR-2, and the results showed that the included 12[26-37] SRs/MAs were of very low quality because none of the included SRs/MAs met the key item 2(none of the included SRs/MAs was a registered protocol);2[38, 39] SRs/MAs were of low quality, and none of the 14 SRs/MAs met key items 7(neither SRs/MAs provided an exclusion list) and item 3(did not explain the reasons for selecting the type of systematic review included in the study design).The methodological quality limitation also included the following items: item 1(1 SR/MA author did not fully describe the PICO elements in the SR),item 8(authors of 2 SRs/MAs did not fully describe essential characteristics of included studies),item 10(2 SRs/MAs did not report funding RCTs/SRs/MAs), item 12(authors of 12 SRs/MAs did not investigate the presence of risk of bias on the total effect),Item 13(4 SRs/MAs authors did not discuss the effect of risk of bias on the total effect of included studies), Item 14(8 SRs/MAs authors did not investigate sources of heterogeneity in results, and/or did not discuss their effect on study results), item 15(authors of 7 SRs/MAs did not test for publication bias, and/or discussed its effect on results), item 16(authors of 2 SRs/MAs did not describe funding sources, and/or statements conflict of interest).The results are summarized in Table 3.

3.3.2 Results of the Risk of Bias Assessment.

Regarding the results of the ROBIS assessment, both Phase 1 and Domain 1 of Phase 2 rated SRs/MAs as having a low risk of bias;In the phase 2, 4 SRs/MAs in Domain 2 were rated as having low risk of bias;8 SRs/MAs in Domain 3 were rated as low risk of bias, 1 SR/MA in Domain 4 was rated as low risk of bias;And all SRs/MAs were rated as high risk of bias in Phase 3. The ROBIS scale evaluation results are shown in Table 4.

3.3.3 Report Quality of the Included SRs/MAs.

17 of the 27 items had a "yes or partial yes" response rate of over 80%, indicating that the report was relatively complete. However, there were also some reported flaws in other projects.The reports for item 5(Methods: Protocol and registration), item 8(Methods: Search), item 15(Risk of bias across studies), and item 24(Funding) were incomplete("Yes or Partial Yes" response rate was less than 50%).The results of the PRISMA checklist assessment are shown in Table 5.

3.3.4 Results of the Quality of the Evidence.

Meta-analysis was performed on the outcome indicators in the study, and the GRADE system was used to evaluate the quality of 86 outcome indicators under different intervention indicators one by one.Of these, 2 were of moderate quality, 23 were of low quality, and 61 were of very low quality. Limitation downgrading due to risk of bias was more common in included studies (n=86), followed by imprecision (n=63), publication bias (n=62), inconsistency (n=43), and indirectness (n=0). See Table 6 for details.

3.3.5 Summary of Results Included.

The outcome measures extracted from the included studies are listed in Table 6.

3.3.5.1 The effective rate in lowering blood pressure.

6[26,27,30-32,38] SRs/MAs reported the effective rate of blood pressure reduction.2[26,27] SRs/MAs reported that acupuncture alone was more effective than CAD in the treatment of EH;4[30-32,38] SRs/MAs reported that acupuncture combined with CAD was more effective than CAD alone in the treatment of EH.

3.3.5.2 The efficacy of improving SBP and DBP.

11[27,29-34,36-39] SRs/MAs reported the efficacy of improving SBP and DBP. 9[27,29,31-33,36-39] SRs/MAs reported that acupuncture alone was more effective in treating EH than CAD or placebo sham acupuncture or no treatment;10[29-34,36-39] SRs/MAs reported that acupuncture combined with lifestyle regulation or CAD was more effective than lifestyle regulation or CAD or placebo sham acupuncture in the treatment of EH.

3.3.5.3 The effect of reducing the magnitude of SBP and DBP.

3[28,35,37] SRs/MAs reported the magnitude of blood pressure reduction of SBP and DBP.3[28,35,37] SRs/MAs reported that acupuncture alone was more effective than CAD or placebo sham acupuncture in the treatment of EH, and reported that the efficacy of acupuncture combined with CAD in the treatment of EH was better than that of CAD alone or placebo sham acupuncture combined with CAD.

3.3.5.4 The effective rate of comprehensive treatment.

3[32-34] SRs/MAs reported the effective rate of comprehensive treatment. 2[32,33] SRs/MAs reported that the efficacy of acupuncture alone in the treatment of EH was better than that of CAD, and reported that acupuncture combined with CAD or behavioral adjustment was better than CAD alone in the treatment of EH.1[34] SR/MA reported that acupuncture combined with TCM decoction Tianma Gouteng Decoction(TMGTD) was more effective than CAD or TMGTD in the treatment of EH.

3.3.5.5 The effective rate of improving symptoms.

2[26,32] SRs/MAs reported the effective rate of symptom improvement. 2[26,32] SRs/MAs reported that the efficacy of acupuncture alone in the treatment of EH was better than that of CAD, and the efficacy of acupuncture combined with CAD in the treatment of EH was better than that of CAD alone.

3.3.5.6 Adverse reactions.

8[28, 31, 32, 35-39] SRs/MAs reported adverse reactions. The main adverse reactions included occasional acupuncture site bleeding, dizziness, headache, cough, nausea, pain, etc., which did not require treatment and resolved spontaneously after rest. Since most studies failed to report adverse reactions in a standard way, quantitative analysis was not performed.

4. Discussion

At present, the main treatment strategy for EH is to give CAD on the basis of life control combined with the risk assessment of hypertension. However, due to drug tolerance, drug side effects, etc., clinicians are also paying more and more attention to the treatment of hypertension by TCM, especially acupuncture.At present, there has been some clinical evidence for acupuncture treatment of hypertension. We systematically searched the existing systematic reviews and meta-analysis, and comprehensively analyzed the existing evidence. The main findings of the study are as follows:

This study is the first overview of systematic reviews of acupuncture for essential hypertension based on RCTs published between 2009 and 2022. Growing evidence suggests that acupuncture can be used as an adjunctive treatment for EH and reduce dependence on CAD.Overall, available evidence suggests that acupuncture alone or a combination of acupuncture and medicine is more effective than placebo (sham acupuncture) or conventional antihypertensive regimens in the treatment of EH. In terms of safety, acupuncture has no serious adverse reactions.

4.1 The methodology is not standardized. The results of the AMSTAR-2 evaluation showed that the methodological quality of the included literature was rated as very low or low, mainly due to the following problems:(1)Missing preliminary design protocol: the researcher should specify the preliminary design protocol in the SRs/MAs. Most of the SRs/MAs included in this article were not registered, which may have increased the risk of bias in the preparation of the systematic reviews;(2)Incomplete literature search: the researchers included in the literature searched at least two databases, but most of them did not conduct supplementary search and gray literature search;(3)Excluded literature list not listed:it may affect the authenticity of the results. During the systematic review process, providing a list of potentially relevant studies that did not meet the inclusion criteria and explaining the reasons for exclusion is an integral part of high-quality SR/MA;(4) Risk of bias analysis assessment flaws: when RCTs of different quality are included, the authors should assess their impact on the study results through subgroup analysis, regression analysis, sensitivity analysis, etc..Some of the included systematic reviews have insufficient or no description of the risk of bias assessment, and the lack of assessment of publication bias may undermine the authenticity of the conclusions;Furthermore, if SRs/MAs does not report funding resources that include RCTs, this may increase clinical trial bias, as findings from industry-funded studies may be biased in favor of funders.

In the GRADE system rating, acupuncture has a certain efficacy in the treatment of EH, but the quality of evidence is low. Because the methodological quality of the 14 included SRs/MAs has certain defects, and the methodological quality of the original studies included in each SR/MA is not high, which affects the strength of the demonstration of the outcome indicators.It also shows that the original research design of the current acupuncture therapy for EH has certain defects, lacks scientific and standardized methodological guidance, and the sample size of the research is relatively small, which ultimately affects the strength of the systematic review.According to the graded evidence quality assessment, 2 of the 86 effect sizes were of moderate quality, 23 were of low quality, and 61 were of very low quality. Risk of bias was the most common downgrading factor, followed by imprecision, publication bias, inconsistency and indirectness.Risk of bias is mainly reflected in the fact that most of the original RCTs on acupuncture for EH did not clearly describe random sequence generation, allocation concealment, or blinding. Through further analysis, the outcome measures included in the SRs/MAs were found to be at risk of publication bias. It is worth noting that almost all SRs/MAs indicated that the addition of acupuncture is an effective treatment, however due to low methodological quality studies, the conclusions of SRs/MAs may differ from real-world results and require further confirmation in the future.

4.2 Implications for future research.

To reduce various biases such as selectivity, implementation, and measurement,for the original research, further large-sample, multi-center, long-term clinical RCTs based on evidence-based medicine standards are needed, and attention should be paid to the correct and reasonable implementation of randomization, allocation scheme concealment and blinding, etc..In addition, to further improve the quality of the evidence, authors should pay attention to the registration of the study protocol to ensure the rigor of its procedures before conducting SRs/MAs studies.In terms of literature search and selection, information on excluded literature and a full search strategy for all databases should be listed and elaborated to ensure transparency[40]. In the quantitative calculation of effect size, care should be taken to exclude the results of individual studies one by one to ensure the stability of the results. In addition, a complete assessment of publication bias would also improve the accuracy of the meta-analysis results[40].

4.3 Strengths and limitations.

Our overview is the first use of AMSTAR-2, ROBIS, PRISMA, and GRADE to assess SRs/MAs regarding acupuncture for EH.The evaluation results strengthen the quality of the current relevant SRs/MAs evidence, and secondly, the evaluation process of AMSTAR-2, ROBIS, PRISMA and GRADE grading revealed the obvious limitations of SRs/MAs and RCTs,which may help guide future high-quality clinical research.However, we must also acknowledge the limitations of this overview. Due to language limitations, this study only included systematic reviews published in both Chinese and English, and did not search Korean and Japanese databases with the same background in traditional Chinese medicine research. At the same time, the retrieval process has not actually carried out manual retrieval, so there is a certain selection bias.In addition, two researchers conducted literature screening and quality assessment, and the process was subjective, and the number of SRs/MAs included was small, and the overall quality was not high.

Declarations

Acknowledgments

We would like to thank the National Natural Science Foundation of China for financial support.

Authors’ Contributions

MXF, XQW,and GHD participated in the research design; MXF, XQW,and GHD conducted a literature search and screened data extraction; MXF,XQW and RML analyzed the data, did a statistical analysis, and wrote the manuscript; MXF, RML, and GHD participated in the correction of the manuscript; All authors reviewed the manuscript. All authors read and approved the final version of the manuscript.

Funding

National Natural Science Foundation of China (No. 82174172, 81774047),National Key R&D Program Project (No.: 2019YFC1710401).

Data Availability

The datasets analyzed during the current study are available from the corresponding author on reasonable request.

Ethics approval and consent to participate：not applicable.

Consent for publication: not applicable.

Competing interests: All authors declare that they have no competing interests.

Authors' information

Maoxia Fan is the first author: student pursuing a PhD degree,Shandong University of Traditional Chinese Medicine(e-mail:[email protected]); Correspondence:^#Guohua Dai,Affiliated Hospital of Shandong University of Traditional Chinese Medicine, No. 16369, Jingshi Road, Lixia District, Jinan City, Shandong Province(e-mail:[email protected]).

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