Parkinson’s disease (PD) is a progressive neurodegenerative disease that is characterized by bradykinesia, resting tremor, rigidity, and postural instability [
In the last decade, exercise interventions, as assisting pharmacological treatments of PD, showed desirable effects on improving balance, gait, and overall functional status of individuals with mild to moderate PD through experience-dependent neuroplasticity [
Therefore, the aim of this systematic review is to summarize and evaluate the evidence on the effectiveness of Tai Chi for PD. And the meta-analyses of Tai Chi for PD were conducted especially on motor function, balance, gait, and quality of life in individuals with PD.
Relevant electronic databases were searched from the earliest date available to June 2014: PubMed, EMBASE, Cochrane Library, Wan Fang Data, Weipu Database for Chinese Technical Periodicals, and China Knowledge Resource Integrated Database (CNKI). The following search terms were used in various combinations: Parkinson’s disease, Parkinson, Parkinsonism, Tai Chi, Taiji, and shadow boxing. And reference lists of relevant systematic reviews and primary studies were manually identified. In order to check for unpublished studies, trial registrations (WHO International Clinical Trials Registry Platform) and dissertations (Chinese Dissertation Full-Text Database and ProQuest Dissertations) were also searched. In addition, we have contacted the experts in the relevant field by e-mails.
The eligible studies must meet the following criteria: (1) study design: randomized controlled trials (RCTs); (2) the target population being diagnosed with PD; (3) types of interventions: Tai Chi compared with any comparator without Tai Chi relevant exercises; (4) the interesting outcomes including motor function, balance, gait, and quality of life; (5) the paper being available in either English or Chinese. The studies are excluded if (1) the primary intervention was Tai Chi plus other exercises; (2) the crossover studies did not report outcomes of the first phase so as to prevent any bias of carryover or order effects; (3) the studies are reported by only abstracts of conference proceedings without the detailed information.
After exclusion of duplicates, eligible studies were identified independently by two authors. Disagreements were resolved by a consensus after discussion. A third author was consulted in case of disagreements to improve accuracy.
For eligible studies, two reviewers independently extracted data based on a predesigned data extraction form including general information (first author, country, and year of publication, sample size, mean age, and Hoehn and Yahr stage of patients with PD), details of the interventions (treatment duration, style and dosage of Tai Chi, and comparison details), and main outcome assessments. The primary author was contacted by e-mails when relevant information was not reported. The authors resolved disagreements by discussions.
The methodological quality of eligible studies was assessed independently by two reviewers using PEDro scale. The PEDro scores ranged from 0 to 10 points, which has a fair-to-good reliability for RCTs of the physiotherapy in systematic reviews [
Meta-analyses were carried out using Cochrane Collaboration software (Rev Man 5.1). In eligible studies, continuous data was combined using more conservative random-effects model for the expected heterogeneity. And standardized mean difference (SMD) and 95% confidence intervals (CI) were calculated in the meta-analyses. The
A total of 118 relevant references were identified by our search strategy. After eliminating duplicate entries, the number of papers was reduced to 88. And 69 references were excluded by screening titles and abstracts. Finally, after assessing full-text papers of the remaining studies, 9 RCTs were included in our review [
Flow chart for this meta-analysis. RCTs: randomized controlled trials.
The principal characteristics of nine eligible studies are presented in Table
Characteristics of randomized controlled trials of Tai Chi for Parkinson’s disease.
First author, year, country | Sample size | Mean age (year) | Hoehn and Yahr stage | Treatment duration (week) | Main outcome |
Experimental group |
Control group |
---|---|---|---|---|---|---|---|
Hackney, 2008, |
33 | 64 | 1.5–3 | 10–13 | UPDRS III, BBS, gait, TUG, six-minute walk | Yang-style Tai Chi |
No intervention |
Hackney, 2009, |
75 | 67 | 1–3 | 13 | PDQ-39 | Yang-style Tai Chi |
(1) Tango |
Li, 2011, |
56 | 68 | 2.5–3 | 8 | UPDRS III, BBS, PDQ-39 | Tai Chi |
Walking |
Zhu, 2011, |
40 | 64 | 1-2 | 4 | UPDRS III, BBS | Tai Chi |
Walking |
Li, 2012, |
195 | 69 | 1–4 | 24 | UPDRS III, gait, TUG, functional-reach test | Tai Chi |
(1) Stretching |
Amano, 2013, |
45 | 66 | 2-3 | 16 | UPDRS III, gait | Yang-style Tai Chi |
(1) Qigong |
Choi, 2013, |
22 | 63 | 1-2 | 12 | UPDRS, TUG, gait, six-minute walk, one-leg standing | Tai Chi |
No intervention |
Nocera, 2013, |
23 | 66 | 2-3 | 16 | Cognitive-executive function, |
Yang-style Tai Chi |
No intervention |
Gao, 2014, |
80 | 69 | 1–4 | 12 | UPDRS III, BBS, TUG | Yang-style Tai Chi |
No intervention |
UPDRS: unified Parkinson’s disease rating scale; BBS: berg balance scale; TUG: timed up and go; PDQ-39: Parkinson’s disease questionnaire-39.
Table
PEDro scales of included randomized controlled trials.
Study | Eligibility criteria | Random allocation | Concealed allocation | Similar at baseline | Subjects blinded | Therapists blinded | Assessors blinded | <15% dropouts | Intention-to-treat analysis | Between-group comparisons | Point measures and variability data | Total |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Hackney and Earhart 2008 [ |
1 | 1 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5 |
Hackney and Earhart 2009 [ |
1 | 1 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5 |
Li 2011 [ |
1 | 1 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 6 |
Zhu et al. 2011 [ |
1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 6 |
Li et al. 2012 [ |
1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 7 |
Amano et al. 2013 [ |
1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 7 |
Choi et al. 2013 [ |
1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 6 |
Nocera et al. 2013 [ |
1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 6 |
Gao et al. 2014 [ |
1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 6 |
0: does not meet the criteria; 1: meets the criteria. Criteria (without eligibility criteria) were used to calculate the total PEDro score.
UPDRS III, clinician-scored monitored motor evaluation, is the most commonly used scale in the clinical study of PD. Seven studies assessed the effects of Tai Chi for PD on motor function by UPDRS III [
Forest plot showing the effect of Tai Chi on unified Parkinson’s disease rating scale III (UPDRS III), timed up and go, and six-minute walk in patients with Parkinson’s disease.
The functional mobility in participants with PD was assessed using the timed up and go test (TUG) in four studies [
Six studies investigated the effect of Tai Chi on balance function in patients with PD [
Forest plot showing the effect of Tai Chi on balance in patients with Parkinson’s disease.
Three studies assessed the effect of Tai Chi on gait function in individuals with PD [
Forest plot showing the effect of Tai Chi on gait in patients with Parkinson’s disease.
Four studies investigated the effectiveness of Tai Chi on quality of life in individuals with PD [
Forest plot showing the effect of Tai Chi on quality of life in patients with Parkinson’s disease.
Only two studies evaluated the follow-up effects of Tai Chi for PD [
The main purpose of this systematic review is to evaluate the evidence of Tai Chi for PD. The primary finding is that there is beneficial evidence of Tai Chi on improving motor function and balance in patients with PD. However, there is no evidence that Tai Chi is more effective on improving gait and quality of life in individuals with PD. And there is not enough evidence on follow-up effects of Tai Chi for PD.
This is a comprehensive systematic review that has evaluated the current evidence in the effect of Tai Chi for PD. In our systematic review, the detailed meta-analyses of Tai Chi for PD were performed on motor function, balance, gait, and quality of life. Hence our systematic review has shown the objective evidence that Tai Chi had better immediate effects on improving motor function and balance in patients with PD. And current reviews are consistent with our findings [
Our main findings are different from the previous reviews [
Tai Chi is beneficial for PD, especially for balance and motor function. This may be related with the improvements on coordination, cognitive function, stepping strategy, and flexibility. In Pei et al.’s study, Tai Chi practitioners showed better eye-hand coordination and movement control [
There are some potential limitations in our review. First, there is the degree of uncertainty in locating relevant studies because of limited retrieving resources, language barrier, and publication bias. Second, there are a small number of eligible studies in current review. It should be noted that there are methodological flaws in these trials. The therapists and patients were not blinded. Moreover, 5 trials used no intervention as a comparator. Although most studies employed blinding assessors to make up for these deficiencies, the bias cannot be avoided due to the placebo effect, which may affect the stability of current results.
In addition, there are statistically significant outcomes in the meta-analyses, but these results should be explained carefully. Tai Chi shows better improvements on motor function than control therapies, but the size of treatment effect is small, especially for UPDRS III. In some meta-analyses, the power is also small due to the small number of eligible studies. The six-minute walk and gait were analyzed based on two trials and three ones, respectively. Moreover, the synthetic results may also be affected by styles (Yang-style, Sun-style, etc.) and parameters (duration, frequency, dosage, etc.) of Tai Chi in our meta-analyses. The current results must be strongly challenged because of insufficient follow-up.
Although Tai Chi shows statistically significant improvements on motor function and balance for patients with PD in the current meta-analyses, there is indeed not enough evidence to conclude that Tai Chi is effective for PD because of the small treatment effect, methodological flaws of the eligible studies, and insufficient follow-up. Consequently, large-scale, high-quality RCTs with long follow-up are warranted to confirm current findings of Tai Chi for PD.
The authors declare that there is no conflict of interests regarding the publication of this paper.