Introduction

Chronic diseases are the leading cause of death in developed and developing countries1. These long-term diseases drastically affect the quality of life of afflicted patients and can cause depression of afflicted patients. Indeed, health-related quality of life (physical, psychological status) is increasingly important in people suffering from chronic diseases. According to the World Health Organization2, more than 36 million people in the world are killed by chronic diseases each year and approximately 80% of these deaths, accounting for 29 million people, are from low- and middle-income countries. The five main types of chronic diseases include cardiovascular and cerebrovascular diseases, chronic respiratory diseases, diabetes, cancers and musculoskeletal disorders2,3,4. Given the prevalence of chronic diseases and mental illnesses, the World Economic Forum concluded that the world would sustain a cumulative output loss of $47 trillion between 2011 and 2030, of which nearly $30 trillion would be attributable to cardiovascular diseases, chronic pulmonary diseases, diabetes and cancers4. Therefore, low-cost, easily accessible and side effect-free programs must be developed to cure such chronic diseases.

Exercise is generally well accepted as significantly contributing to the prevention and treatment of chronic diseases5. Traditional Chinese exercise (TCE) is a representative form of exercise that is becoming increasingly popular worldwide for the improvement of health and well-being. TCE such as Tai Chi, Qigong and Baduanjin does not require the use of equipment, is low in cost and easy to learn6,7,8. TCE has been used for 2000 years and is also a promising9, low-risk intervention that can help improve quality of life and alleviate depression in patients with chronic diseases10,11,12.

TCE includes different types of exercise; the main types are Tai Chi, Qigong, Baduanjin and Liuzijue, among others. Tai Chi, which is also called “taiji,” “taijichuan” or “taijiquan,” is a famous form of TCE worldwide. Tai Chi is a type of traditional mind body exercise, that developed as a martial art and a means of self-defense in China. Qigong is a general form of TCE and comprises exercises for postural control, coordinated breathing and meditation. Qi refers to vital energy and gong means discipline. Baduanjin translates to the Eight Section Brocades, which refers to eight individual movements for improving general health. Liuzijue is a form of breathing exercise in China that was passed down from ancient times6,7,8,9,10,11,12,13. The practice of TCE usually focuses on a combination of physical and mental exercises.

Most TCE is not only exercise therapy, but also includes meditation field. Because of the meditative aspect, TCE could also improve psychological well-being and reduce stress. According to Chang et al.14, TCE (e.g., Tai Chi) is theorized to improve cognition by enhancing brain activation through meditation. In addition, Wayne et al.15 had proposed a relationship between Tai Chi and social interaction and this positive linkage has even extended to brain function. Based upon the model of Chang et al.14, TCE could bring positive efficacy in cognition via multiple pathways, including motor function, cardiovascular function, coordination function, social interaction and meditation.Although TCE is widely performed to prevent and treat chronic diseases, studies on TCE have not reached a consensus with regard to how such exercise can improve the quality of life and alleviate depression in patients with chronic diseases10,11,12,16,17. Similarly, we have yet to find any meta-analysis that has assessed the effect of TCE on the quality of life and depression of patients with chronic diseases. Previous systematic reviews have focused on one type of TCE (such as Tai Chi) for chronic diseases. Therefore, this current meta-analysis aims to identify the effects of TCE on the quality of life and depression of patients with chronic diseases. Additionally, the meta-analysis provides an overall assessment of the effect of TCE on the quality of life and mental health of patients with chronic diseases as well as of the different TCE methods used to treat people with chronic diseases.

Methods

Protocol and registration

The meta-analysis was performed and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines. The protocol was registered prior to conducting the review. Systematic review registration: http://www.crd.york.ac.uk/PROSPERO. PROSPERO registration number: CRD42013006474.

Search strategy

We searched for relevant studies that were published between January 1957 and January 2015 from several electronic data sources, including PubMed, EMBASE, Web of Science, the Cochrane Library, EBSCO (CINAHL) and China National Knowledge Infrastructure. No language restrictions were employed. The search was limited to randomized controlled trials (RCTs). All of the electronic search strategies for all databases are provided in Supplementary Table S1.

Inclusion criteria

  1. 1

    Types of studies: We only covered published articles with completed RCTs.

  2. 2

    Types of participants: We included articles wherein the participants suffered from five main clusters of chronic diseases: cardiovascular and cerebrovascular diseases (e.g., stroke and heart attacks), musculoskeletal disorders (e.g., fibromyalgia), chronic respiratory diseases (i.e., chronic obstructed pulmonary disease), cancers and diabetes.

  3. 3

    Types of interventions: We only considered articles that compared an intervention group, in which the members performed TCE (e.g., Tai Chi, Qigong and Baduanjin), with a control group, in which the members performed another intervention (i.e., strength exercise or drug) or that did not undergo any intervention.

  4. 4

    Types of outcome measures: The outcome measures were quality of life and depression. Outcomes were recorded for three time periods: short term (less than 3 months), mid term (from 3 months to 12 months) and long term (1 year or more).

Selection of studies

Two authors independently used the same selection criteria to screen the titles, abstracts and bodies of the relevant articles. The studies that failed to meet the inclusion criteria were removed from the sample. In the case of disagreement, the two authors would discuss or consult a third author.

Data extraction and management

The following data were extracted from the selected articles: study characteristics (e.g., author and year), participant characteristics (e.g., age and number of subjects), intervention description, trial period duration, assessed outcomes and time points. The two authors who selected the studies also extracted the data from the included articles. Any disagreement was resolved through discussion and a third author was consulted in cases where disagreement persisted.

Quality assessment

We used the PEDro scale18 to evaluate the risk of bias for inclusion in the meta-analysis. Using a pre-determined 10-item scale, two review authors independently assessed the methodological quality of each study. The following information was evaluated: random allocation, concealed allocation, baseline comparability, blind subjects, blind therapists, blind assessors, adequate follow-up, intention-to-treat analysis, between-group comparisons, point estimates and variability. The review authors did not evaluate their own studies. A third author was consulted when a disagreement occurred.

Statistical analysis

Review Manager software (RevMan5.3) was used to conduct the meta-analysis. The chi-square test and I2 statistic were used to evaluate the heterogeneity among the studies. Using a random effects model, the outcome measures from the individual studies were combined through a meta-analysis. If continuous data were reported as the median and within an interquartile range (IQR), the median would be assumed to be equivalent to the mean and the relationship of the IQR with the standard deviation was roughly SD = IQR/1.3519. Given that all variables in the included studies were expressed as continuous data, we used the standardized mean difference or the mean difference and the 95% confidence interval (CI) to analyze the studies. We considered p < 0.05 as statistically significant. Sensitivity analysis was performed by removing each study individually to assess the consistency and quality of the results. Funnel plot asymmetry was employed to assess possible publication bias by Egger’s regression test.

Results

Descriptive results

The flow chart of the study selection procedure is outlined in Fig. 1. Of the 106 potentially relevant studies that were identified, 46 were excluded for not completing an RCT or for producing irrelevant outcomes. Thus, we included 4311 patients with chronic diseases from the 60 remaining articles20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79 (21 articles focused on musculoskeletal disorders, 16 articles focused on cardiovascular diseases, 14 articles focused on diabetes, 4 articles focused on cancers, 4 articles focused on chronic respiratory diseases and 1 article focused on chronic physical illnesses). These articles were mainly published in China (n = 21, 35%), USA (n = 15, 25%), Australia (n = 4, 6.67%), Sweden (n = 3, 5%), Korea (n = 3, 5%), Hong Kong (n = 3, 5%), the UK (n = 2, 3.33%), Canada (n = 2, 3.33%), Germany (n = 2, 3.33%), New Zealand (n = 1, 1.67%), Israel (n = 1, 1.67%) and Japan (n = 1, 1.67%). The characteristics of each included study are summarized in Table 1.

Table 1 Characteristics of included studies.
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Figure 1
figure 1

Flow chart of the study selection procedure.

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Methodological quality

The methodological quality of all included articles was assessed (Table 2). The generation of the allocation sequence was reported in all articles (n = 60, 100%). A total of 15 articles (25%) conducted allocation concealment. A total of 23 articles (38.33%) blinded the outcome assessors to the treatment allocation. A total of 28 articles (46.67%) had an adequate follow-up period. In addition, 13 articles (21.67%) used the intention to treat as their primary analysis method.

Table 2 Risk of bias assessment of included studies.
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Quality of life

Short-form (SF-36) survey

Using a random effects model, the meta-analysis of six studies35,39,49,62,67,76 with 591 patients showed that TCE could improve the total SF-36 score in the short term [SMD (95% CI) = 0.59 (0.32, 0.87), P < 0.001] (Table 3) and mid term [SMD (95% CI) = 0.61 (0.16, 1.05), P = 0.008] (Table 3). The meta-analysis of 22 studies with 1533 patients26,27,29,34,35,41,44,46,49,51,52,54,55,56,58,59,63,64,65,76,78,79 that were suitable for inclusion showed that TCE had a significant positive effect on the SF-36 physical function subscale in the short term [SMD (95% CI) = 0.35 (0.13, 0.56), P = 0.002] (Table 3 and Fig. 2) and mid term [SMD (95% CI) = 0.49 (0.12, 0.85), P = 0.009] (Table 3 and Fig. 3). A total of 22 studies with 1502 patients20,27,29,34,35,42,44,46,49,51,52,54,55,56,58,59,63,64,65,76,78,79 were included to estimate the effect of TCE on the SF-36 mental health subscale. The TCE group outperformed the control group in terms of the SF-36 mental health subscale in the short term ([SMD (95% CI) = 0.28 (0.11, 0.46), P = 0.002) (Table 3, Supplementary Figure S1) and mid term [SMD (95% CI) = 0.39 (0.08, 0.71), P = 0.02] (Table 3, Supplementary Figure S2). No significant difference was observed among the 15 studies with 935 patients20,26,27,29,34,41,46,49,54,55,59,63,65,76,79 that investigated the SF-36 general health subscale in the short term ([SMD (95% CI) = 0.15 (−0.00, 0.31), P = 0.06] (Table 3, Supplementary Figure S3) and mid term [SMD (95% CI) = 0.05 (−0.24, 0.34), P = 0.73] (Table 3, Supplementary Figure S4). A sensitivity analysis was performed for the total SF-36 score, the SF-36 physical function subscale, the SF-36 mental health subscale, the SF-36 general health subscale, the significance of the results was not changed when studies were removed one by one.

Table 3 Summary of results.
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Figure 2
figure 2

Meta-analyses of traditional Chinese exercises on short form-36 physical function at the short term.

SD = standard deviation; 95% CI = 95% confidence intervals; IV = inverse variance.

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Figure 3
figure 3

Meta-analyses of traditional Chinese exercises on short form-36 physical function at the mid-term.

SD = standard deviation; 95% CI = 95% confidence intervals; IV = inverse variance.

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General Health Questionnaire (GHQ)

Two studies22,57 were included to estimate the effect of TCE on the GHQ. The TCE group outperformed the control group in terms of improving the GHQ in a random effects model [SMD (95% CI) = −0.68 (−1.26, −0.09), P = 0.02] (Table 3).

WHO quality of life (WHOQOL)

The meta-analysis of four studies23,31,53,60 with 287 patients that were suitable for inclusion revealed that TCE had a significant positive effect on the WHOQOL general health subscale [SMD (95% CI) = 0.68 (0.04, 0.47), P = 0.04]. However, TCE did not have a significant effect on the WHOQOL physical health subscale [SMD (95% CI) = 0.13 (−0.59, 0.85), P = 0.73] or the WHOQOL psychological health subscale [SMD (95% CI) = 0.22 (−0.04, 0.47), P = 0.09] (Table 3). The results were affected by one study60 for WHOQOL general health, one study53 for WHOQOL physical health and one study53 for WHOQOL psychological health in the sensitivity analysis. Therefore, the meta analysis provided weak evidence of the effects of TCE on the WHOQOL.

Depression

Center for Epidemiologic Studies Depression Scale (CES-D)

Eight studies24,25,51,55,56,58,69,78 with 508 patients were included to estimate the effect of TCE on the CES-D. TCE could improve the CES-D in the short term [SMD (95% CI) = −0.86 (−1.42, −0.31), P = 0.002] (Table 3 and Fig. 4A) and mid term [SMD (95% CI) = −0.41 (−0.64, −0.18), P < 0.001] (Table 3 and Fig. 4B). Sensitivity analysis revealed that the pooled result was stable when studies were removed one by one.

Figure 4
figure 4

Meta-analyses of traditional Chinese exercises on Center for Epidemiologic Studies Depression Scale.

A: in the short term. B: in the mid-term. SD = standard deviation; 95% CI = 95% confidence intervals; IV = inverse variance.

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Self-rating depression scale (SDS)

The meta-analysis of five studies30,33,40,72,75 with 315 patients that were suitable for inclusion found that TCE had a significant effect on the SDS in the short term [SMD (95% CI) = −0.6 (−0.83, −0.36), P < 0.001] (Table 3, Supplementary Figure S5 A). Sensitivity analysis found that the pooled result was not influenced by individual trials.

Beck Depression Inventory (BDI)

Three studies26,31,43 with data from 180 patients were included to assess the effect of TCE on the BDI. TCE had a non-significant positive effect on the BDI in a random effects model [SMD (95% CI) = −0.15 (−0.75, 0.44), P = 0.61] (Table 3). The significance of the result was changed in the sensitivity analysis when one study26 was removed, this result offered inferior evidence for the effect of TCE on BDI.

Profile of Mood States-Depression (POMS-D)

Three studies68,70,71 with data from 156 patients were used to estimate the effect of TCE on the POMS-D. TCE could improve the POMS-D in the short term (SMD (95% CI) = −1.64 (−2.55, −0.73), P < 0.001) (Table 3, Supplementary Figure S5 B). Sensitivity analysis indicated that the pooled result was not influenced by individual trials.

Hamilton Depression Scale (HAMD)

The meta-analysis of three studies37,61,73 with 189 patients that were suitable for inclusion indicated that TCE had a significant effect on the HAMD in the short term [SMD (95% CI) = −1.36 (−1.97, −0.75), P < 0.001] (Table 3, Supplementary Figure S5 C). Sensitivity analysis revealed that the pooled result was stable when studies were removed one by one.

Symptom Checklist-90 (SCL-90)

Four studies21,38,74,77 presenting data from 284 patients were included to assess the effect of TCE on the SCL-90. The result showed that TCE improved the SCL-90 [SMD (95% CI) = −0.7 (−1.32, −0.08), P = 0.03] (Table 3). Sensitivity analysis indicated that the pooled result was not influenced by individual trials.

Publication bias

The results of the Egger’s regression test did not reveal any publication bias for the total SF-36 (asymmetry test P = 0.128), SF-36 physical function (asymmetry test P = 0.207), the SF-36 mental health subscale (asymmetry test P = 0.678), the SF-36 general health subscale (asymmetry test P = 0.906) and the CES-D (asymmetry test P = 0.361).

Discussion

Summary of findings

Several types of TCE are used to prevent and treat chronic diseases. However, the extant systematic reviews primarily focus on either one type of disease (e.g., cardiovascular disease) or one type of TCE (e.g., Tai Chi). In this review and meta-analysis, we combined all of the evidence from the numerous relevant studies evaluating the various forms of TCE into one review to assess the overall effect of TCE on patients with chronic diseases.

We gathered information on 4311 subjects from 60 articles that provided evidence on the effects of TCE on improving the quality of life and alleviating depression in patients with chronic diseases. The meta-analysis revealed that TCE had a significant positive effect on the quality of life (SF-36 physical function, SF-36 mental health, SF-36 total, GHQ and WHOQOL general health) and depression (CES-D, SDS, POMS-D, HMAD, SCL-90) in patients with chronic diseases. Therefore, TCE had a significant clinical effect on improving the quality of life and reducing depression in patients with chronic diseases. We used the chi-square test and I2 statistic to assess the heterogeneity among the studies and identified obvious heterogeneity for some outcomes. To solve this problem, sensitivity analysis was conducted for to assess the consistency and quality of the results. Sensitivity analysis revealed that most of the pooled results (SF-36, CES-D, SDS, POMS-D, HAMD, SCL-90) were stable when studies were removed one by one. But the significance of the result (WHOQOL, BDI) was changed through sensitivity analysis, these results offered inferior evidence for the effect of TCE on WHOQOL and BDI.Because TCE does not require the use of equipment, the exercises are low in cost and easy to learn. Chronic patients who performed TCE demonstrated considerable improvements in their conditions80,81. According to the theory of Traditional Chinese medicine, TCE could help one’s body to dredge the meridians and collaterals, facilitate blood circulation, relax the mind, balance emotion and regulate the internal organs to enhance one’s physical health and quality of life and to improve one’s psychological state6. TCE generally combines postural control, breath regulation and mediation. The primary benefit of TCE stems from the holistic nature and TCE benefits both physical and psychosocial health. However, the exact mechanism by which TCE affects patients with chronic diseases is complex and remains unclear. Thus, further evidence on the mechanism by which TCE affect chronic diseases should be obtained.

Strengths and limitations

Relevant articles were searched from a wide range of electronic databases (e.g., PubMed, EMBASE, Web of Science and Cochrane Library). Considering that TCE originated in China, we searched for relevant information from the largest Chinese information database. The current study was the first meta-analysis to estimate the effects of TCE on the quality of life and depression of patients with chronic diseases by comparing an intervention group with a no intervention group. Given that the selected articles were published in America, Asia, Europe and Oceania, the results of this study may be generalizable to most parts of the world. Furthermore, most of the included articles were published over the last five years (from 2010 to 2015). To reduce bias and transcription errors, two authors independently performed the study selection, data extraction and quality assessment processes.

Nevertheless, our meta-analysis had several limitations. First, although all of the included articles were RCTs, only 15 studies (25%) reported how the patient allocation was concealed. According to the intention-to-treat principle, 13 articles (21.67%) used the intention to treat as their primary analysis method. A total of 23 articles (38.33%) blinded the outcome assessors to the treatment allocation. Second, the outcome assessors could not be blinded for the comparison between the TCE group and the no-intervention group, therefore generating potential performance and response biass. Third, most articles had no long-term follow-up period (over one year). Therefore, we did not conduct a meta-analysis to estimate the long-term effect of TCE on chronic diseases. Fourth, we used Egger’s regression test to assess publication bias. Additionally, we systematically searched several electronic databases for publications. Although we found no publication bias, we did not search for any unpublished trials. Fifth, due to the lack of studies with training time ranging from 6 months to 12 months, especially 12 months, we did not perform a subgroup meta analysis focusing on exercise training time. Sixth, some studies included in our meta analysis had small sample sizes. Future meta-analyses including more large-scale, high-quality RCTs are required to obtain further proof of the effects of TCE. Seventh, most of the Chinese studies from our meta analysis were not registered in the international clinical trials registry platform of the World Health Organization. To reduce bias, all studies should be performed in accordance with the standards of clinical trials (e.g., the Consolidated Standards of Reporting Trials statement).

Implications for policy and practice

Traditional medicine/exercise, including TCE is an important and often underestimated part of health services worldwide82. TCE is extensively performed in most countries; however, in many countries and regions, the public, medical professionals and healthcare policymakers remain confused about the effectiveness, safety and quality of TCE. In our meta-analysis, we identified both the scientific and clinical importance of TCE. Unlike other exercises, TCE may contribute to improving the quality of life (e.g., SF-36 and GHQ) and reducing depression (e.g., CESD, SDS, BDI) in patients with chronic diseases. These findings provide useful information for chronic disease patients, medical professionals and healthcare policymakers. As public health professionals, we believe that healthcare policymakers and medical professionals must consider how TCE improves the health of patients with chronic diseases.

Implications and future research

Further evidence from larger and better quality studies must be collected to determine the effects of TCE on chronic diseases. Most of the articles with small sample sizes that were included in our meta-analysis only observed patients over a short-term follow-up period. Multicenter RCTs with large sample sizes must be conducted to validate the effects of TCE in patients with chronic diseases. Future studies should improve their methodological standards in the following aspects: random allocation, allocation concealment, long-term follow-up, intention-to-treat analysis and assessor blinding. Likewise, such studies should adhere to generally accepted standards for reporting clinical trials (e.g., the Consolidated Standards of Reporting Trials statement). To estimate the duration of TCE-induced improvements, long-term follow-up periods must be adopted in future studies. In addition, the long-term effectiveness of TCE for patients with chronic diseases must be estimated.

Additional Information

How to cite this article: Wang, X. et al. Effect of traditional Chinese exercise on the quality of life and depression for chronic diseases: a meta-analysis of randomised trials. Sci. Rep. 5, 15913; doi: 10.1038/srep15913 (2015).