Tai Chi for Chronic Obstructive Pulmonary Disease (COPD): An Overview of Systematic Reviews

Figures & data

Figure 1 Flow diagram of literature search.

Table 1 Characteristics of Systematic Reviews

Author/Year/Country	Language	Number of RCTs Included	Quality Assessment Tool for Original Studies Included in SR	Intervention	Comparisons	Data Analysis Methods	Outcomes	Conclusions of the Author
Shao^Citation24/2016/China	Chinese	9 RCTs	The Cochrane Handbook 5.1.0	Tai Chi quan exercise or combined with other interventions with routine drug treatment	Conventional medical treatment	Meta-analysis	FEV1%; FEV1; FEV1/FVC(%)	Tai Chi quan group was superior to conventional drug treatment group in improving lung function FEV1 and FEV1%, but there was no significant difference in FV1/FVC%. The results show that Tai Chi quan exercise can improve pulmonary function in stable COPD patients.
Tian et al^Citation25 /2015/China	Chinese	5 RCTs	The Jadad Scale	Tai Chi training	General treatment or other effective targeted treatment	Meta-analysis	FEV1; FEV1%; FEV1/FVC(%); 6MWT; GRQ	In FEV1, there were significant differences between Tai Chi quan intervention group and control group, but in FEV1%, FVC, FEV1/FVC (%) and 6MWT quality-of-life (SGRQ score) there were no significant differences between the two groups.
Wang et al^Citation26 2015/China	Chinese	6 RCTs	The Jadad Scale	Tai Chi training	Regular activities or routine health guidance	Meta-analysis	FEV1; FEV1% FEV1/FVC(%); 6MWT	Exercise could improve the lung function and exercise endurance in old patients with stable chronic obstructive pulmonary disease, and has positive rehabilitation effects.
Guo et al^Citation30/2015/Canada	English	15 RCTs	The Cochrane Collaboration’s Risk of Bias	Tai Chi training	Other type of treatment (drug therapy, routine activities, and respiratory training)	Meta-analysis	6MWT; FEV1; FEV1%; SGRQ FEV1% GRQ	Tai Chi may improve exercise capacity in the short-, mid-, and long-erms. However, no significant long term differences in pulmonary function and quality-of-life were observed for patients with chronic obstructive pulmonary disease.
Ngai et al^Citation11/2016/China	English	12 RCTs	The Cochrane Handbook for Systematic Reviews of Interventions	Tai Chi	Usual care or another intervention	Meta-analysis	FEV1; FEV1%; SGRQ FEV1/FVC(%); 6MWT	When Tai Chi was compared with other interventions alone, there was no additional impact on the symptoms or physical and mental improvement of COPD patients.
Wu et al^31/2014/China	English	11 RCTs	The Cochrane Handbook for Systematic Reviews of Interventions	Tai Chi	Exercise (aerobics, strength training, or breathing exercises	Meta-analysis	6MWD SGRQ	Preliminary evidence suggests that Tai Chi has beneficial effects on exercise capacity and HRQoL in COPD patients. This exercise can be recommended as an effective alternative training modality in pulmonary rehabilitation programs.
Yan^32/2013/China	English	8 RCTs	The Jadad scale	Tai Chi or Tai Chi Qigong with or without other treatments	Any type of control	Meta-analysis	6MWD; FEV1; FEV1%	Findings suggest that TC may provide an effective alternative means to achieve results similar to those reported following participation in pulmonary rehabilitation programs.
Guo et al^33/2020/China	English	16 RCTs	Cochrane risk of bias assessment tool	Tai Chi or Qigong with routine treatment	Routine treatment with or without exercise	Meta-analysis	FEV1; FEV1%; SGRQ; 6MWT FEV1/FVC (%);	Tai Chi may represent an appropriate alternative or complement to standard rehabilitation programs. However, whether Tai Chi is better than pulmonary rehabilitation exercise has not been determined.
Chen et al^Citation34/2015/Canada	English	4 RCTs	The Physiotherapy Evidence Database (PEDro) scale	Tai Chi training	Other treatments or another exercise intervention	Meta-analysis	6MWT	The results demonstrated a favorable effect or tendency of Tai Chi to improve physical performance and showed that this type of exercise could be performed by individuals with different chronic conditions, including COPD, HF and OA.
Wang and Gao^Citation27 /2020/China	Chinese	16 RCTs	Cochrane risk of bias assessment tool	Tai Chi training with or without other treatment	Other treatments or no intervention	Meta-analysis	FEV1, FEV1%, FEV1/FVC%, 6MWD	Tai Chi exercise can effectively improve the lung function of elderly patients, so that the patient’s breathing is better and smoother, and the exercise capacity is significantly improved.
Wang and Zhou^Citation28 /2020/China	Chinese	9 RCTs	The Jadad scale	Tai Chi training with or without other treatment	No intervention, or aerobics, or respiratory training	Meta-analysis	FEV1, FEV1/FVC%, 6MWD, SGRQ	Taijiquan can effectively improve the motor ability, pulmonary function and quality-of-life of COPD patients.
Dong et al^Citation29 /2021/China	Chinese	15 RCTs	Cochrane risk of bias assessment tool	Tai Chi alone	No limitations with intervention	Meta-analysis	6MWD	Taijiquan exercise intervention in the stale period of the elderly patients with chronic obstructive pulmonary disease rehabilitation effect is significant.

Table 2 The Results of AMSTAR 2

Items	Shao^Citation24	Tian et al^Citation25	Wang et al^Citation26	Guo et al^Citation30	Ngai et al^Citation11	Wu et al^Citation31	Yan^Citation32	Guo et al^Citation33	Chen et al^Citation34	Wang and Gao^Citation27	Wang and Zhou^Citation28	Dong et al^Citation29
I1	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
I2	Y	N	N	Y	Y	N	N	N	N	N	N	N
I3	N	N	N	N	N	N	N	N	N	N	N	N
I4	Y	N	Y	Y	Y	Y	Y	Y	N	N	Y	N
I5	PY	PY	PY	PY	PY	PY	Y	Y	Y	Y	Y	N
I6	Y	Y	PY	Y	Y	Y	Y	Y	Y	Y	N	Y
I7	N	N	N	N	Y	Y	N	N	N	N	N	N
I8	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
I9	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
I10	Y	PY	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
I11	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
I12	Y	N	N	Y	Y	Y	Y	N	N	N	N	N
I13	Y	N	N	Y	Y	Y	Y	N	N	N	N	N
I14	Y	N	N	Y	Y	Y	Y	Y	Y	Y	N	Y
I15	N	Y	N	Y	Y	N	N	N	Y	Y	N	N
I16	N	PY	Y	Y	Y	Y	Y	Y	Y	N	N	N
Ranking of quality	Critically low	Critically low	Critically low	Low	Low	Critically low	Critically low	Critically low	Critically low	Critically low	Critically low	Critically low

Abbreviations: Y, yes; PY, partial yes; N, no.

Table 3 The Result of ROBIS

Signaling Questions of ROBIS	Shao^Citation24	Tian et al^Citation25	Wang et al^Citation26		Guo et al^Citation30			Ngai et al^Citation11		Wu et al^Citation31		Yan^Citation32			Guo et al^Citation33	Chen et al^Citation34		Wang and Gao^Citation27	Wangand Zhou^Citation28	Dong et al^Citation29
1.1 Does the question addressed by the review match the target question?	Y	Y	Y		Y			Y		Y		Y			Y	Y		Y	Y	Y
2.1.1(Q1) Did the review adhere to pre-defined objectives and eligibility criteria?	Y	PY	PY		Y			PY		PY		PY			PY	PY		PY	PY	PY
2.1.2(Q2) Were the eligibility criteria appropriate for the review question?	Y	Y	Y		Y			Y		Y		Y			Y	Y		Y	Y	Y
2.1.3(Q3) Were eligibility criteria unambiguous?	Y	Y	Y		Y			Y		Y		Y			Y	Y		Y	Y	Y
2.1.4(Q4) Were any restrictions in eligibility criteria based on study characteristics appropriate (eg, date, sample size, study quality, outcomes measured)?	Y	Y	Y		Y			Y		Y		Y			Y	Y		Y	Y	Y
2.1.5(Q5) Were any restrictions in eligibility criteria based on sources of information, appropriate (eg publication status or format, language, availability of data)?	Y	Y	Y		Y			Y		Y		Y			Y	Y		Y	Y	Y
Concerns regarding specification of study eligibility criteria	Low	Low	Low		Low			Low		Low		Low			Low	Low		Low	Low	Low
2.2.1(Q6) Did the search include an appropriate range of databases/electronic sources for published and unpublished reports?	Y	N	N		Y			Y		Y		N			Y	Y		N	Y	Y
2.2.2(Q7) Were methods additional to database searching used to identify relevant reports?	Y	Y	N		N			Y		Y		N			N	Y		PY	N	N
2.2.3(Q8) Were methods additional to database searching used to identify relevant reports?	Y	PN	N		Y			Y		Y		N			Y	Y		N	Y	NI
2.2.4(Q9) Were restrictions based on date, publication format, or language appropriate?	Y	Y	Y		Y			Y		Y		Y			Y	N		PY	Y	NI
2.2.5(Q10) Were efforts made to minimise error in selection of studies?	Y	PY	Y		NI			Y		NI		Y			Y	Y		Y	Y	N
Concerns regarding methods used to identify and/or select studies	Low	High	High		Unclear			Low		Unclear		High			Low	Low		High	High	High
2.3.1(Q11) Were efforts made to minimise error in data collection?	Y	Y	NI		Y			Y		Y		Y			Y	N		Y	PY	N
2.3.2(Q12) Were sufficient study characteristics available for both review authors and readers to be able to interpret the results?	Y	Y	Y		Y			Y		Y		Y			Y	Y		Y	Y	Y
2.3.3(Q13) Were all relevant study results collected for use in the synthesis?	Y	Y	Y		Y			Y		Y		Y			Y	Y		Y	Y	Y
2.3.4(Q14) Was risk of bias (or methodological quality) formally assessed using appropriate criteria?	Y	PN	PN		Y			Y		Y		PN			Y	Y		Y	Y	Y
2.3.5(Q15) Were efforts made to minimise error in risk of bias assessment?	Y	Y	Y		Y			Y		Y		Y			Y	Y		Y	Y	N
Concerns regarding methods	Low	High	High		Low			Low		Low		High			Low	Low		Low	Low	High
2.4.1(Q16) Did the synthesis include all studies that it should?	Y	Y	PN		PY			Y		Y		PN			Y	Y		PY	Y	Y
2.4.2(Q17) Were all pre-defined analyses reported or departures explained?	Y	PY	Y		Y			Y		Y		Y			Y	Y		Y	N	Y
2.4.3(Q18) Was the synthesis appropriate given the nature and similarity in the research questions, study designs and outcomes across included studies?	Y	PY	Y		Y			Y		Y		Y			Y	Y		Y	N	Y
2.4.4(Q19) Was between-study variation (heterogeneity) minimal or addressed in the synthesis?	Y	Y	N		Y			Y		Y		Y			Y	Y		Y	N	Y
2.4.5(Q20) Were the findings robust, eg, as demonstrated through funnel plot or sensitivity analyses?	N	Y	N		Y			Y		Y		Y			N	Y		Y	N	N
2.4.6(Q21) Were biases in primary studies minimal or addressed in the synthesis?	Y	Y	N		Y			Y		Y		Y			Y	Y		Y	Y	Y
Concerns regarding the synthesis and findings	High	Low	High		Low			Low		Low		High			Low	Low		Low	High	Low
Phase 3: Judging risk of bias
3.1(Q22) Did the interpretation of findings address all of the concerns identified in Domains 1 to 4?	Y			N		N	NI		Y		NI		N	Y			Y	N	N	N
3.2(Q23) Was the relevance of identified studies to the review’s research question appropriately considered?	Y			Y		Y	Y		Y		Y		Y	Y			Y	Y	Y	Y
3.3(Q24) Did the reviewers avoid emphasizing results on the basis of their statistical significance?	Y			Y		Y	Y		Y		Y		Y	Y			Y	Y	Y	Y
Risk of bias in the review	Low			High		High	Unclear		Low		Unclear		High	Low			Low	High	High	High

Abbreviations: Y, yes; PY, probably yes; PN, probably no; N, no; NI, no information; Q, signaling questions.

Table 4 Reporting Quality Assessment of Systematic Reviews by PRISMA

Section	Items	Shao^Citation24	Tian et al^Citation25	Wang et al^Citation26	Guo et al^Citation30	Ngai et al^Citation11	Wu et al^Citation31	Yan^Citation32	Guo et al^Citation33	Chen et al^Citation34	Wang and Gao^Citation27	Wang and Zhou^Citation28	Dong et al^Citation29
Title	I1 Title	Y	Y	Y	Y	N	Y	N	Y	Y	Y	Y	Y
Abstract	I2 Structured sumary	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
Introduction	I3 Rationale	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I4 Objectives	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
Methods	I5 Protocol and registration	N	N	N	Y	N	N	N	N	N	N	N	N
	I6 Eligibility criteria	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I7 Information sources	Y	Y	Y	Y	Y	Y	Y	Y	NA	NA	Y	Y
	I8 Search	Y	NA	NA	Y	Y	Y	NA	Y	Y	Y	Y	Y
	I9 Study selection	Y	NA	N	N	Y	N	Y	Y	Y	N	N	N
	I10 Data collection process	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I11 Data items	NA	NA	NA	NA	Y	NA	NA	NA	N	N	Y	Y
	I12 Risk of bias in individual studies	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I13 Summary measures	Y	Y	N	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I14 Synthesis methods	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I15 Risk of bias across studies	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I16 Additional analyses	Y	N	N	NA	Y	Y	Y	N	N	Y	NA	Y
Results	I17 Study selection	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I18 Study characteristics	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I19 Risk of bias within studies	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	120 Results of individual studies	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I21 Synthesis of results	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I22 Risk of bias across studies	N	NA	N	Y	Y	N	NA	NA	N	N	N	Y
	I23 Additional analysis	Y	N	NA	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I25 Limitations	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
	I26 Conclusions	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
Funding	I27 Funding	Y	N	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y
Total score		24	19	18	24	25	23	21	23	22	22	22	25
Completion rate		89%	70%	67%	89%	93%	85%	78%	85%	81%	81%	81%	93%

Abbreviations: Y, yes; N, no; NA, not applicable.

Table 5 Summary of the Results of GRADE

Outcomes	Author	Mean Difference or Std. Mean difference (95% CI), P-value	No of Participants (Studies)	Heterogeneity	Quality of the Evidence (GRADE)
FEV1	Shao^Citation24	0.09 (0.03, 0.15), P=0.02*	381 (6 studies)	I^2=0%, P=0.74	⊕⊕⊕⊝ Moderate^a
	Tian et al^Citation25	0.09 (0.04, 0.13), P<0.0001*	229 (4 studies)	χ^2=3.15, P=0.37	⊕⊝⊝⊝ Very low^a,b,c
	Wang et al^Citation26	0.02 (−0.10, 0.14), P=0.76	200 (2 studies)	I^2=0%, P=0.39	⊕⊕⊝⊝ Low^a,b,c
	Guo et al^Citation30	0.04 (−0.03, 0.12), P=0.26 (≤3 months)	425 (4 studies)	I^2=0%, P=0.74	⊕⊕⊝⊝ Low^a,b
		0.10 (0.01, 0.19), P=0.03* (6 months)	524 (6 studies)	I^2=62%, P=0.02	⊕⊕⊕⊝ Moderate^c
		0.03 (−0.08, 0.14), P=0.59 (≥12 months)	96 (2 studies)	I^2=0%, P=0.08	⊕⊝⊝⊝ Very low^a,b,c
	Ngai et al^Citation11	0.11 (0.02, 0.20), P=0.012*	258 (4 studies)	I^2=0%, P=0.59	⊕⊕⊕⊝ Moderate^a
	Guo et al^Citation33	0.13 (0.06, 0.20), P=0.0002* (≤3 months)	219 (3 studies)	I^2=12%, P=0.32	⊕⊕⊝⊝ Low^a,b,c
		0.15 (0.08, 0.21), P=0.01* (4–6 months)	136 (3 studies)	I^2=59%, P=0.09	⊕⊝⊝⊝ Very low^a,b,c
FEV1	Wang and Gao^Citation27	0.46 (0.20, 0.72), P<0.01*	1,492 (17 studies)	I^2=29.5%, P>0.05	⊕⊝⊝⊝ Very low^a,b,c,d
	Wang and Zhou^Citation28	0.74(0.09, 1.38), P<0.00001*	539 (9 studies)	I^2=22.3%, P=0.28	⊕⊝⊝⊝ Very low^a,b,c,d
	Dong et al^Citation29	−0.02 (−0.08, 0.04), P<0.00001*	383 (5 studies)	I^2=0%, P=0.77	⊕⊝⊝⊝ Very low^a,b
FEV1%	Shao^Citation24	0.09 (0.04, 0.13), P<0.0001*	374 (7 studies)	I^2=50%, P=0.06	⊕⊕⊝⊝ Low^a,b,c
	Tian et al^Citation25	0.14 (−2.77, 3.52), P=0.81	158 (3 studies)	χ^2=0.66, P=0.72	⊕⊝⊝⊝ Very low^a,b,c
	Wang et al^Citation26	4.95 (0.33, 9.57), P=0.04*	220 (3 studies)	I^2=56%, P=0.10	⊕⊝⊝⊝ Very low^a,b,c
	Ngai et al^Citation11	1.33 (−4.25, 6.91), P=0.64	527 (5 studies)	I^2=80%, P=0.0004	⊕⊝⊝⊝ Very low^a,b,c
	Guo et al^Citation33	0.22 (−1.80, 2.23), P=0.83 (≤3 months)	142 (2 studies)	I^2=0%, P=0.56	⊕⊕⊝⊝ Low^a,b,c
FEV1%	Guo et al^Citation33	3.33 (−1.17, 7.84), P=0.15 (4–6 months)	96 (2 studies)	I^2=30%, P=0.23	⊕⊕⊝⊝ Low^a,b,c
		5.78 (−3.75, 15.31), P=0.07 (>6 months)	234 (2 studies)	I^2=073%, P=0.05	⊕⊝⊝⊝ Very low^a,b,c
	Wang and Gao^Citation27	0.35 (0.21, 0.48), P<0.01*	939 (12 studies)	I^2=37%, P>0.05	⊕⊝⊝⊝ Very low^a,b,c,d
FEV1/FVC%	Shao^Citation24	0.02 (−0.10, 0.14), P=0.76	313 (5 studies)	I^2=63%, P=0.03	⊕⊝⊝⊝ Very low^a,b,c
	Tian et al^Citation25	−0.09 (−1.34, 1.15), P=0. 88	319 (5 studies)	χ^2=0.46, P=0.98	⊕⊕⊝⊝ Low^a,b,c
	Wang et al^Citation26	4.62 (0.73, 8.51), P=0.02*	227 (4 studies)	I^2=43%, P=0.15	⊕⊕⊝⊝ Low^a,b,c
	Guo et al^Citation30	1.50 (–3.17, 6.17), P=0.53 (≤3 months)	260 (5 studies)	I^2=78%, P=0.001	⊕⊕⊝⊝ Low^a,b,c
		0.35 (−1.22, 1.92), P=0.66 (6 months)	156 (3 studies)	I^2=0%, P=0.97	⊕⊕⊝⊝ Low^a,c
FEV1/FVC%	Guo et al^Citation30	2.13 (−1.73, 5.99), P=0.28 (>6 months)	96 (2 studies)	I^2=0%, P=0.91	⊕⊝⊝⊝ Very low^a,b,c
	Ngai et al^Citation11	5.35 (−0.93, 11.64), P=0.095	120 (3 studies)	I^2=61%, P=0.08	⊕⊕⊕⊝ Moderate^a
	Guo et al^Citation33	3.33 (−2.92, 9.58), P=0.3 (≤3 months)	120 (3 studies)	I^2=61%, P=0.08	⊕⊕⊝⊝ Low^a,b,c
	Wang and Gao^Citation27	0.51 (0.05, 0.97), P<0.05*	661 (12 studies)	I^2=86.7%, P<0.01	⊕⊝⊝⊝ Very low^a,b,c,d
	Wang and Zhou^Citation28	0.57 (0.19, 0.96), P<0.00002*	593 (6 studies)	I^2=81%, P<0.00001	⊕⊝⊝⊝ Very low^a,b,c,d
6MWD	Tian et al^Citation25	50.9 (−45.7, 147.51), P=0.3	123 (2 studies)	χ^2=15.14, P<0.0001	⊕⊝⊝⊝ Very low^a,b,c
	Wang et al^Citation26	33.81 (6, 61.41), P=0.02*	326 (5 studies)	I^2=87%, P<0.0001	⊕⊕⊝⊝ Low^a,c
	Guo et al^Citation30	16.02 (2.86, 29.17), P=0.02* (≤3 months)	302 (4 studies)	I^2=50%, P=0.06	⊕⊕⊝⊝ Low^a,c
6MWD	Guo et al^Citation30	30.90 (6.88, 54.93), P=0.01* (6 months)	464 (5 studies)	I^2=82%, P=0.002	⊕⊕⊝⊝ Moderate^a,c
	Guo et al^Citation28	24.63 (2.30, 46.95), P=0.03* (≥12 months)	94 (2 studies)	I^2=0%, P=0.64	⊕⊝⊝⊝ Very low^a,b,c
	Ngai et al^Citation11	29.64 (10.52, 48.77), P=0.0024*	318 (6 studies)	I^2=59%, P=0.03	⊕⊕⊝⊝ Moderate^a
	Wu et al^Citation31	39.99 (15.63, 56.35). P=0.0005*	456 (4 studies)	I^2=86%, P<0.00001	⊕⊕⊕⊝ Moderate^a
	Yan^Citation32	34.22 (21.25, 47.20), P<0.00001*	306 (3 studies)	I^2=0%, P=0.38	⊕⊕⊝⊝ Low^a,c
	Guo et al^Citation33	24.29 (6.29, 42.28), P=0.008* (≤3 months)	363 (6 studies)	I^2=77%, P=0.0006	⊕⊕⊝⊝ Low^a,c
		37.35 (3.96, 70.75), P=0.03* (4–6 months)	76 (2 studies)	I^2=70%, P=0.007	⊕⊝⊝⊝ Very low^a,b,c
6MWD	Guo et al^Citation33	47.73 (−14.96, 110.42), P=0.14 (>6 months)	96 (2 studies)	I^2=77%, P=0.04	⊕⊝⊝⊝ Very low^a,b,c
	Chen et al^Citation34	1.58 (0.01, 0.73), P=0.05	368 (3 studies)	I^2=61%, P=0.08	⊕⊕⊝⊝ Low^a,c
	Wang and Gao^Citation27	20.35 (16.95, 23.95), P<0.01*	1,630 (20 studies)	I^2=88.8%, P<0.01	⊕⊝⊝⊝ Very low^a,b,c,d
	Wang and Zhou^Citation28	0.78 (0.30, 1.26), P<0.00001*	531 (7 studies)	I^2=84%, P<0.00001	⊕⊝⊝⊝ Very low^a,c,d
	Dong et al^Citation29	57.3 (39.42, 75.17), P<0.00001*	532 (8 studies)	I^2=75%, P=0.00002	⊕⊕⊝⊝ Low^a,c
SGRQ	Tian et al^Citation25	−0.93 (−5.53, 3.67), P=0.69	130 (2 studies)	χ^2=0.19, P=0.67	⊕⊝⊝⊝ Very low^a,b,c
	Guo et al^Citation28	−6.58 (−11.87, −0.64), P=0.02* (≤3 months)	485 (5 studies)	I^2=64%, P=0.02	⊕⊕⊕⊝ Moderate^c
		−2.01 (−5.74, 1.73), P=0.29 (6 months)	312 (3 studies)	I^2=0%, P=0.88	⊕⊕⊕⊝ Moderate^a
SGRQ	Yan^Citation32	−4.08 (−7.52, −0.64), P=0.02*	366 (3 studies)	I^2=24%, P=0.27	⊕⊕⊝⊝ Low^a,c
	Guo et al^Citation33	−0.19 (−4.57, 0.72), P=0.15 (≤3 months)	525 (4 studies)	I^2=38%, P=0.19	⊕⊕⊕⊝ Moderate^c
	Wang and Zhou^Citation28	−0.25 (−0.41, −0.09), P=0.003*	624 (8 studies)	I^2=68%, P=0.003	⊕⊝⊝⊝ Very low^a,c,d

Notes: GRADE Working Group grades of evidence: High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate. ⊕⊕⊕⊝: The evidence is rated as “moderate” quality; ⊕⊕⊝⊝: “low” quality; ⊕⊝⊝⊝: “very low” quality. ^aNo mention of blind and allocation concealment; ^bThe optimal sample size is not reached. ^cThere was a huge heterogeneity between the included original studies. ^dThere was a huge problem of statistics. *P<0.05. The value of P<0.05 is considered significant.

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