Table 2.
Methodological quality assessment of included studies.
| Study | Bias arising from the randomization process | Bias due to deviations from the intended interventions | Bias due to missing outcome data | Bias in the measurement of the outcome | Bias in the selection of the reported result | Overall bias |
| Xiong 2007[20] | Moderate | High | Low | High | Low | Moderate |
| Jin 2009[21] | Moderate | High | Low | High | Low | Moderate |
| Ma 2010[22] | Moderate | High | Low | High | Low | Moderate |
| Teng 2014[23] | Moderate | High | Low | High | Low | Moderate |
| Zheng 2014[24] | Moderate | High | Low | High | Low | Moderate |
| Li 2014[25] | Moderate | High | Low | High | Low | Moderate |
| Zhang 2015[26] | Moderate | High | Low | High | Low | Moderate |
| Wu 2017[27] | Moderate | High | Low | High | Low | Moderate |
| Wang 2019[28] | Moderate | High | Low | High | Low | Moderate |
| Tang 2019[29] | Moderate | High | Low | High | Low | Moderate |
| Han 2020[30] | Moderate | High | Low | High | Low | Moderate |
| Zhang 2020[31] | Moderate | High | Low | High | Low | Moderate |
| Li 2010[32] | Moderate | High | High | High | Low | Moderate |
| Chen 2020[33] | Moderate | High | Low | High | Low | Moderate |
| Huang 2020[34] | Moderate | High | Low | High | Low | Moderate |
| Ming 2020[35] | Moderate | High | Low | High | Low | Moderate |