Table 2.

Assessment of the risk of bias for included non-randomised studies

	Confounding	Selection bias	Classification bias of interventions	Deviations from intended interventions	Bias due to missing data	Measurement bias	Report bias	Overall
Chen et al. [35]	Serious	Serious	Serious	Moderate	Low	Low	Moderate	Serious
De Pascale et al. [36]	Serious	Serious	Serious	NI	Low	Low	Moderate	Serious
Di Carlo et al. [42]	Serious	Serious	Serious	Moderate	Low	Low	Moderate	Serious
Geng et al. [37]	Serious	Serious	Serious	NI	Low	Low	Moderate	Serious
Ibrahim et al. [38]	Serious	Serious	Serious	NI	Low	Low	Moderate	Serious
Maseda et al. [39]	Critical	Critical	Serious	Serious	Low	Low	Moderate	Critical
Moreno et al. [34]	Serious	Serious	Serious	Serious	Low	Low	Moderate	Serious
Vardakas et al. [40]	NI	NI	Serious	NI	Low	Low	Moderate	NI
Wu et al. [41]	Serious	Serious	Serious	Serious	Low	Low	Moderate	Serious