Risk of bias assessment
A risk of bias assessment was performed by 2 reviewers (X.Z. and M.S.). It was evaluated according to the Newcastle-Ottawa Scale, which consists of 8 items with a maximum of 9 stars. Studies judged ≥7 stars were considered as low risk, ≥5 as relatively low risk, and ≤ 4 as high risk. High risk on assessment was not a reason for exclusion.