Table 2:

Quality assessment of included studies

Author; Year	Item 1	Item 2	Item 3	Item 4	Item 5	Item 6	Item 7	Item 8	Item 9	Item 10	Item 11	Item 12	Item 13	Item 14
NIH risk of bias tool
Alfaraj; 2019
Arabi; 2017
Auyeung; 2005
Chen; 2006
Jia; 2009
Liu; 2020
Meng; 2003
Song; 2003
Wang; 2004
Wu; 2020
Yam; 2007
Zha; 2020
Zhou; 2020
Wang; 2020
Cochrane risk of bias tool
Lee; 2004								NA	NA	NA	NA	NA	NA	NA

, Low risk; , High risk; , Unclear; NA: Not applicable.

Items for National Heart Lung and Blood Institute risk of bias tools: 1. Was the research question or objective in this paper clearly stated?; 2. Was the study population clearly specified and defined?; 3. Was the participation rate of eligible persons at least 50%?; 4. Were all the subjects selected or recruited from the same or similar populations (including the same time period)? Were inclusion and exclusion criteria for being in the study prespecified and applied uniformly to all participants?; 5. Was a sample size justification, power description, or variance and effect estimates provided?; 6. For the analyses in this paper, were the exposure(s) of interest measured prior to the outcome(s) being measured?; 7. Was the timeframe sufficient so that one could reasonably expect to see an association between exposure and outcome if it existed?; 8. For exposures that can vary in amount or level, did the study examine different levels of the exposure as related to the outcome (e.g., categories of exposure, or exposure measured as continuous variable)?; 9. Were the exposure measures (independent variables) clearly defined, valid, reliable, and implemented consistently across all study participants?; 10. Was the exposure(s) assessed more than once over time?; 11. Were the outcome measures (dependent variables) clearly defined, valid, reliable, and implemented consistently across all study participants?; 12. Were the outcome assessors blinded to the exposure status of participants?; 13. Was loss to follow-up after baseline 20% or less?; 14. Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure(s) and outcome(s)?

Items for Cochrane risk of bias tools: 1. Random sequence generation. 2. Allocation concealment; 3. Blinding of participant and personnel; 4. Blinding of outcome assessor; 5. Incomplete outcome data; 6. Selective reporting; 7. Other bias