Description of the condition
Cardiovascular diseases (CVD) are a variety of conditions that affect the heart and blood vessels. They are the number one cause of death and disability worldwide and were responsible for 17.3 million global deaths in 2008; in 2010, CVD accounted for 35% of total deaths in the USA and UK, 38% in China (WHO 2011a).
The development of strategies to prevent CVD have become a public health priority, especially since the prevalence and burden of CVD is increasing worldwide (WHO 2011a). The focus of such strategies are modifiable lifestyle factors such as diet, smoking habits, exercise and stress. Whilst clinical treatments are effective in preventing and treating CVD, other strategies involving a healthy lifestyle and stress management have also been shown to be beneficial (Frishman 2005). One potentially beneficial strategy that involves both stress management and exercise is qigong.
Description of the intervention
Qigong was developed in China several thousand years ago and is a meditative practice used in health promotion. The three main components of qigong are mind regulation, body regulation and breath regulation (Chow 2012) and it uses gentle, focused exercises for the body and mind to increase and restore the flow of Qi (a pivotal life energy) with the aim of encouraging and accelerating the body's ability to heal itself (Lee 2009). This flow of Qi is thought to be vital for optimal vitality and physical and emotional health (Chow 2012). There are many styles of qigong. These include: Baduanjin which is a low level aerobic exercise characterised by eight fine delicate movements, stretching and controlled breathing (Chyu 2011); Guolin which contains a slow walking exercise with slight twisting waist movements and arm movements (Jones 2001); and Dantian qigong which is characterised by a focus on breathing exercises, slow controlled movements and meditation (von Trott 2009). The therapeutic effects of qigong vary according to style (Chow 2012). Furthermore, each style of qigong falls into two distinct forms: internal and external qigong. Internal qigong is self-directed and is performed without the aid of a teacher or therapist. It involves meditation, breathing, focusing attention and movement in order to achieve optimal health (Ernst 2008; Lee 2007; Park 2011). External qigong, on the other hand, involves qigong practitioners who will direct their Qi energy into the patient in order to cure disease or alleviate symptoms (Ernst 2008; Lee 2007).
Interest in complementary therapies, such as qigong, is growing for the prevention of disease and maintenance of health (Kraft 2009). Moreover, complementary therapies which involve exercise are increasingly popular in the elderly, and as such may be an important strategy for the primary and secondary prevention of CVD. Qigong is practiced by 60 million people each day in China (Chow 2012), and is one of the most recommended exercises for patients with coronary artery disease (Davis 2009). There have been a number of studies that have shown qigong to be effective for reducing blood pressure (Davis 2009; Nahas 2008), reducing triglyceride levels and fasting cholesterol (Innes 2008; Lee 2004) and having a beneficial effect on type 2 diabetes (Xin 2007). Data also suggests that qigong may be beneficial in decreasing levels of perceived stress (Lee 2003; Skoglund 2007) which is a determinant of CVD (WHO 2011b). Qigong has been shown to reduce catecholamine and cortisol levels in response to stressors compared to a placebo group (Guo 1996).
How the intervention might work
As with tai chi and yoga, qigong incorporates both exercise and stress reduction, both of which are important in the prevention of CVD. There is an abundance of research to suggest that exercise is important in preventing diabetes and CVD (Bassuk 2005; Mittal 2008; Press 2003). The exact mechanisms for this are unknown however, some potential mechanisms include enhancing insulin sensitivity and fibrinolytic and endothelial function, enhancing glycaemic control, reducing hypertension, regulating body weight, reducing insulin resistance, and reducing atherogenic dyslipidaemia and inflammation (Bassuk 2005).
Qigong has an additional benefit in that it has been found to help reduce stress (Bronas 2009), which is also a determinant of CVD. Again, the exact mechanisms in which qigong does this are unknown but some suggest that qigong reduces sympathetic stimulation which lowers the levels of catecholamines and stress hormones circulating in the body (Bronas 2009; Guo 1996).
Why it is important to do this review
To date, there are few randomised controlled trials (RCTs) that have investigated the effectiveness of qigong for CVD prevention, and fewer systematic reviews. One systematic review of interest, looked at the effectiveness of qigong for hypertension and found that regular qigong practice helped to lower blood pressure in those with hypertension (Lee 2007). This was similar to the findings of Guo 2008, which reported that internal qigong was effective in decreasing blood pressure in those with essential hypertension when compared to no-treatment controls but was not as effective as drug controls or conventional exercise controls. One other systematic review examined the effectiveness of qigong for type 2 diabetes; however, the authors found that there was insufficient information to determine if qigong was effective for this population (Lee 2009).
None of the above systematic reviews directly focus on CVD prevention and other CVD risk factors (Guo 2008; Lee 2007; Lee 2009). Therefore, a comprehensive systematic review is needed which thoroughly examines interventions involving qigong in healthy adults or those at increased risk of CVD to determine the effectiveness of qigong for the primary prevention of CVD.
To determine the effectiveness of qigong for the primary prevention of CVD.
Criteria for considering studies for this review
Types of studies
All RCTs including cross-over trials. We will include cross-over trials in this review by using data only from the first half as a parallel group design.
Types of participants
Adults aged 18 years and over from the general population and those at high risk of CVD. We will exclude those who have experienced a previous myocardial infarction (MI), stroke, revascularisation procedure (coronary artery bypass grafting (CABG) or percutaneous transluminal coronary angioplasty (PTCA)), those with angina, or angiographically defined coronary heart disease (CHD).
Types of interventions
Trials investigating any style of qigong (internal or external).
Studies will be stratified by qigong style and duration. Multi-factorial lifestyle intervention trials will not be included in this review in order to avoid confounding. Furthermore, we will focus on follow-up periods of six months or more as these are the most relevant to public health interventions, but will consider trials of at least three months follow-up where these are lacking.
Trials will only be considered where the comparison group is either no intervention or minimal intervention (e.g. leaflets promoting physical activity or other more general forms of health promotion but no face-to-face interaction)
Types of outcome measures
- Cardiovascular mortality
- All-cause mortality
- Non-fatal endpoints such as MI, CABG, PTCA, angina, angiographically defined CHD, stroke, carotid endarterectomy, peripheral arterial disease (PAD)
- Changes in blood pressure (systolic and diastolic blood pressure) and blood lipids (total cholesterol, high-density lipid (HDL) cholesterol, low-density lipid (LDL) cholesterol, triglycerides)
- Occurrence of type 2 diabetes as a major CVD risk factor
- Health-related quality of life
- Adverse effects
Search methods for identification of studies
We will search the following databases: MEDLINE, EMBASE, the Web of science (Science Citation Index Expanded (SCI-EXPANDED), Social Sciences Citation Index (SSCI), Conference Proceedings Citation Index - Science (CPCI-S), AMED, NHS Centre for Reviews and Dissemination (CRD) databases, the Cochrane Library (including the Cochrane Central Register of Controlled Trials (CENTRAL), Health Technology Assessment (HTA) Database, Database of Abstracts of Reviews of Effects (DARE) and NHS Economic Evaluation Database (NEED)), and OpenGrey.
Medical subject headings (MeSH) or equivalent and text word terms will be used. Searches will be designed in accordance with the Cochrane Heart Group methods and guidance, and will be tailored to individual databases. The search strategy for MEDLINE is shown in Appendix 1. We will apply a search filter for randomised controlled studies to the MEDLINE search and adapt it for use in EMBASE and the Web of Science (Higgins 2011).
There will be no language restrictions.
Searching other resources
We will also check reference lists of reviews and retrieved articles for additional studies.
We will search the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com/mrct), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry platform (ICTRP) search portal (http://apps.who.int/trialsearch/) for ongoing trials.
We will perform citation searches on key articles and use Google Scholar to search for further studies.
We will contact experts in the field for unpublished and ongoing trials, and contact authors where necessary for any additional information.
Data collection and analysis
Selection of studies
Two authors (LH, NF) will review the title and abstract of each paper and retrieve potentially relevant references. We will than obtain the full text of potentially relevant studies and two authors (LH, NF) will independently select studies to be included in the review by using pre-determined inclusion criteria. In all cases we will resolve disagreements about study inclusion by consensus and consult a third author (KR/EE) if disagreements persist.
Data extraction and management
Two authors (LH, NF) will independently extract data using a pre-standardised data extraction form. We will also contact chief investigators to provide additional relevant information if necessary. Details of the study design, participant characteristics, study setting, intervention and outcome data (including details of outcome assessment, adverse effects and methodological quality (randomisation, blinding and attrition)) will be extracted from each included study. We will resolve disagreements about extracted data by consensus and consult a third author (KR/EE) if disagreements persist.
Assessment of risk of bias in included studies
We will assess risk of bias by examining the random sequence generation and allocation concealment, description of drop-outs and withdrawals (including analysis by intention-to-treat), blinding (participants, personnel and outcome assessment) and selective outcome reporting in each trial as per the guidance in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Two authors (LH, NF) will independently assess the risk of bias of included studies and will rate each domain as having a low risk of bias, a high risk of bias or an unclear risk of bias.
Measures of treatment effect
We will process data in accordance with the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Dichotomous outcomes will be expressed as odds ratios (ORs) or relative risks (RRs) with 95% confidence intervals (CIs) calculated for each study. For continuous outcomes net changes will be compared (i.e. intervention group minus control group differences) and a weighted mean difference (WMD) or standardised mean difference (SMD) and 95% CIs calculated for each study.
Assessment of heterogeneity
We will conduct tests of heterogeneity for each outcome (using the chi
Subgroup analysis and investigation of heterogeneity
We will stratify results by style and duration of qigong exercise where possible. Trials will also be stratified by baseline risk i.e. healthy participants vs. participants at high risk of CVD. If possible we will also examine the effects of age and gender.
We will carry out sensitivity analysis by excluding studies with a high risk of bias. If there are sufficient trials, funnel plots and tests of asymmetry will be undertaken to assess possible publication bias (Egger 1997).
No acknowledgements to date at the protocol stage.
Appendix 1. MEDLINE search strategy
1. exp Cardiovascular Diseases/
14. atrial fibrillat*.tw.
17. (sick adj sinus).tw.
18. exp Stroke/
19. (stroke or stokes).tw.
21. cerebral vascular.tw.
23. (brain adj2 accident*).tw.
24. ((brain* or cerebral or lacunar) adj2 infarct*).tw.
25. exp Hypertension/
27. peripheral arter* disease*.tw.
28. ((high or increased or elevated) adj2 blood pressure).tw.
29. exp Hyperlipidemias/
36. exp Arteriosclerosis/
37. exp Cholesterol/
39. "coronary risk factor* ".tw.
40. Blood Pressure/
41. blood pressure.tw.
43. Breathing Exercises/
45. (Qi-gong or qi gong).tw.
46. (Chi chung or Chi gong or Chi Kung).tw.
47. (Qi Kung or Jhi gong or Chi gung or Qi chung).tw.
48. (ch'i kung or kung ch'i).tw.
50. randomized controlled trial.pt.
51. controlled clinical trial.pt.
54. drug therapy.fs.
58. 50 or 51 or 52 or 53 or 54 or 55 or 56 or 57
59. exp animals/ not humans.sh.
60. 58 not 59
61. 42 and 49 and 60
Contributions of authors
All authors contributed to protocol development.
Declarations of interest
Sources of support
- Warwick Medical School, University of Warwick, UK.
- Peninsula Medical School, Exeter, UK.
- NIHR Cochrane Programme Grant, UK.