Table 5.

Risk of bias assessment for included non-RCTs according to the Newcastle–Ottawa Scale

Study	Representativeness of the exposed cohort	Selection of the nonexposed cohort	Ascertainment of exposure	Outcome of interest not present at the start of the study	Comparability of cohorts on the basis of the design or analysis	Assessment of outcome	Sufficient follow-up for the outcome to occur	Adequacy of follow-up	Total
Wismeijer et al. 2014	★	★	★	★	★	☆	★	★	7
Schepke et al. 2015	☆	★	★	★	★	☆	★	★	6
Delize et al. 2019	☆	★	★	★	★	☆	★	★	6
Pan et al. 2019	☆	★	★	★	★	☆	★	★	6
Guo et al. 2019	☆	★	★	★	★	☆	★	★	6
Koulivand et al. 2020	☆	★	★	★	★	☆	★	★	6
Di Fiore et al. 2018	☆	★	★	★	★	☆	★	★	6
Gherlone et al. 2016	☆	★	★	★	☆	☆	★	★	5