Risk of Bias Assessment
For the included observational studies, the results of the risk-of-bias assessment tool are presented in Appendix Figures S1 and S2. Moderate risk of bias was mainly raised in the “Bias due to confounding”, “Bias in measurement of outcomes”, and “Bias in the selection of reported result” domains in almost all studies. Only in a single study30 serious risk of bias was raised in the “Bias in the selection of reported result” domain, because the authors didn’t provide all their results.