The therapeutic effects of qigong in patients with chronic obstructive pulmonary disease in the stable stage: a meta-analysis

Two investigators (H. Tong and Y. Liu) found eligible articles through a systematic search. They independently searched databases such as EMBASE, PubMed, Web of Science, Cochrane, WangFang data, China National Knowledge Infrastructure, and VIP Database for Chinese Technical Periodicals, without the upper-limit time until October 8, 2017, without any language restrictions. The following search terms were used: “Qigong”, “Ch’i Kung”, “Yindao”, “Gongfa”, “Baduanjin”, “Eight brocade”, “Yijinjing”, “Five Animals Exercise”, “Liuzijue”, “Six Character Formula”, “Daoyin yangsheng gong”, “Shierduanjin”, “12 brocade”, “Big dance”, “Mawangdui guidance”, “Tai Chi stick”, “Tai Chi staff”, “COPD” and “chronic obstructive pulmonary disease”. The detailed search strategy is in Additional file 1. The styles of Qigong that we finally selected were recommended by the Health Qigong Administrative Center of the General Administration of Sport of China (Beijing, China; details are in Additional file 2).

After removing repetitive articles, two investigators (H. Tong and Y. Liu) reviewed the abstracts independently. Studies were eliminated if they were reviews, meta-analyses, observational studies, case reports, case series, letters to the editor, comments, or irrelevant. Randomized controlled trials (RCTs) were included if the human participants were diagnosed as having stable COPD. [26] Studies were included if patients had participated in Qigong exercises longer than 6 months after diagnosis. However, trials were excluded if Qigong was combined with other similar energy practices, such as yoga techniques and meditation. Meanwhile, the control group only received conventional therapy such as routine health guidance and/or drug treatments. [27] Then, we searched the full articles for further assessment; articles without full text versions available were excluded. Any disagreements between the two investigators (H. Tong and Y. Liu) would refer to the third-party member’s opinion (Y. Zhu).

The primary outcomes used to evaluate the effect of Qigong were the 6MWD, FEV1, FEV1/FVC, FEV1/pre, Monitored Functional Task Evaluation, COPD Assessment Test for exercise, Short Form-36 Health Quality Survey (SF-36) for General Health, and SF-36 for Mental Health. We emailed authors to request any missing data needed for our analysis. The differences between the control and experimental groups were evaluated by the effect sizes and 95% confidence intervals (CIs), which were calculated in Review Manager (version 5.3). As to continuous data, mean differences (MDs) were estimated. The I² statistics reflected heterogeneity as follows: I² = 0% indicated no heterogeneity; I² = 0–25% indicated low heterogeneity; I² = 25–50% indicated mild heterogeneity; I² = 50–75% indicated moderate heterogeneity; and I² = 75–100% indicated high heterogeneity. [28] Funnel plot would be used to reflect the potential publication bias if there were more than ten studies.

We used the Cochrane Handbook for Systematic Reviews of Interventions to assess the quality and risk of bias for each selected article. Two authors (H. Tong and Y. Liu) reviewed all selected articles and reported their evaluations as “high,” “low,” or “unclear” for the following items: (1) selection bias; (2) blinding; (3) attrition bias; (4) reporting bias; (5) other biases. [29] To improve accuracy, any disagreements would refer to a third member’s opinion. The quality and risk-of-bias assessments were described in Additional file 3.

Figure 1 shows the flow diagram of the selection process. All databases yielded 346 potentially relevant articles. Sixty-nine duplicate studies were eliminated. After screening the abstracts, 255 studies were excluded based on their titles and summaries. There were 22 eligible studies for full-text screening; 10 studies were subsequently selected for the final analysis. Details of the excluded articles are provided in Additional file 4.

Among the 10 studies [25, 30‐38] selected for this meta-analysis, four studies [25, 30‐32] were published in English, and six studies [33‐38] were published in Chinese, two of which were dissertations. [37, 38] The period in which these studies were published was from 2010 to 2016. The number of participants ranged from 22 individuals to 148 individuals, and the total number of participants was 993 individuals. The Qigong exercises used were Baduanjin in five studies, [25, 33, 35‐37] Liuzijue in two studies, [31, 34] and Yijinjing in two studies. [32, 38] One study [30] used reproduced Qigong derived from the aforementioned three types of Qigong and Wuqinxi. More details are provided in Table 1.

Eight [25, 30‐33, 36‐38] of the 10 trials used the 6MWD test to evaluate the effect of Qigong and compared a patient group with a control group. One trial [36] chose 24 weeks and 36 weeks as the observation time points. We chose the 36-week timepoint because 24 weeks is slightly less than 6 months. We used the different types of Qigong to establish subgroups in our analysis.

The random effects analysis was conducted to merge the results because eight studies [25, 30‐33, 36‐38] had high heterogeneity (I² = 90%). The effect size of the eight studies found that Qigong was associated with an improvement in 6MWD test results significantly compared to the control intervention (MD, 30.57 m; 95% CI, 19.61–41.53 m; P < 0.00001; Fig. 2). Baduanjin resulted in the best improvement in the 6MWD (MD, 43.51 m; 95% CI, 37.88–49.13 m; P < 0.00001; Fig. 2). The other three exercise types also resulted in significant improvements in the 6MWD: Yijinjing (MD, 31.05 m; 95% CI, 26.96–35.14 m; P < 0.00001); Liuzijue (MD, 10.60 m; 95% CI, 5.33–15.98 m; P = 0.0001); and reproduced Qigong (MD, 27.39 m; 95% CI, 16.49–38.29 m; P < 0.00001).

Five [32, 34‐36, 38] of the 10 trials used FEV1 to evaluate the effect of Qigong in COPD patients. The random effects analysis was conducted to incorporate results because the combined trials had high heterogeneity (I² = 90%). We used the different styles of Qigong to establish subgroups. The effect size of the five trials [32, 34‐36, 38] showed that Qigong could significantly improve the FEV1 (MD, 0.32; 95% CI, 0.09–0.56; P < 0.001; Fig. 3). Yijinjing, which was used in 2 trials, [32, 38] resulted in the best improvement in the FEV1 (MD, 0.59; 95% CI, 0.38–0.80; P < 0.00001; Fig. 3). Baduanjin also had a good effect (MD, 0.25; 95% CI, 0.14–0.36; P < 0.00001; Fig. 3). One trial, [34], which used Liuzijue, did not show a positive effect. Six [30, 32, 34‐36, 38] of the 10 trials used the FEV1/FVC to assess the improvement in lung function. A fixed effects analysis was conducted to incorporate the results (I² = 47%). The effect size of the six trials [30, 32, 34‐36, 38] showed that Qigong could significantly improve the FEV1/FVC (MD, 2.66; 95% CI, 1.32–2.26; P = 0.0001; Fig. 4). Yijinjing showed a treatment effect (MD, 4.39; 95% CI, 1.84–6.93; P = 0.0007; Fig. 4), and Baduanjin also improved the FEV1/FVC (MD, 4.32; 95% CI, 1.95–6.68; P = 0.0003; Fig. 4). However, Liuzijue and reproduced Qigong did not have significant effects. Five trials [31, 32, 35, 36, 38] used the FEV1/pre to assess the improvement in lung function (MD, 6.04 CI, 2.58–9.5; P = 0.006; Fig. 5). The random effects analysis was conducted to pool the results together (I² = 61%). Yijinjing showed the best results (MD, 8.76; 95% CI, 2.49–15.03; P = 0.006; Fig. 5). Baduanjin resulted in a significant improvement (MD, 6.48; 95% CI, 2.77–10.19; P = 0.0006; Fig. 5), but Liuzijue did not result in a significant improvement (MD, 0.13; 95% CI, − 5.34 to 5.60; P = 0.96; Fig. 5).

Two [25, 31] of the 10 studies used the Monitored Functional Task Evaluation to assess the activities of daily living for COPD patients in the stable stage. The effect of the two trials showed that Qigong resulted in a significant improvement in the Monitored Functional Task Evaluation results compared to the control group (MD, 0.88; 95% CI, 0.78–0.99; P < 0.00001; Fig. 6). There were three trials [32, 35, 38] that used the COPD Assessment Test for exercise to evaluate the severity of COPD. This assessment revealed that Qigong significantly improved the COPD assessment test results for exercise in COPD patients (MD, − 5.54; 95% CI, − 9.49 to − 1.59; P = 0.006; Fig. 6). Two trials [25, 31] used the SF-36 for General Health and the SF-36 for Mental Health to evaluate physical and psychological health, respectively. The general health results showed that Qigong resulted in a significant improvement for COPD patients (MD, 5.22; 95% CI, 3.65–6.80; P < 0.00001; Fig. 6). However, there was no statistic difference in mental health (MD, − 1.21; 95% CI, − 2.75 to 0.33; P = 0.12; Fig. 6). We did not conduct subgroup analyses in this study because of the small number of trials.

There were likewise some limitations in our meta-analysis. First, although there were 10 RCTs involving 993 individuals selected by us, the sample size of each study was relatively small. Meanwhile, all involved studies were conducted in China, and clinical studies should also be conducted in Western countries to evaluate the effect of Qigong, especially in different ethnicities. Moreover, we searched eight databases but did not search for unpublished trials. Finally, there was apparent heterogeneity because of the differences in the four selected types of Qigong, and we then used the types to generate subgroups in addition to analysing them collectively; not all studies used the same test index, and some of them only had one group in subgroup analysis. Therefore, it is necessary to update the data in the future when there have been more RCTs conducted.