Quality assessment and data collection
Two independent reviewers (R.V. and J.H.) performed a systematic quality assessment for all eligible studies using the Newcastle-Ottawa Scale (NOS), and data collection of the included studies10. Discrepancies were resolved by discussion and consensus between the reviewers.
The NOS evaluates the study’s quality based on three perspectives (i.e., selection, comparability, and outcome), with three domains each. A maximum overall score of 9 points could be obtained, indicating that the study is comparable to a well-designed double-arm cohort study. Studies assessed with an overall score of 5 or lower, indicating a high risk of bias, were excluded from the review as decided during the protocol stage.