Table 2.

Robins-I scale for the risk of bias assessment of non-randomized studies.

	D1	D2	D3	D4	D5	D6	D7	Overall Judgement
Cavaignac E., et al., 2017 [48]	Serious	Low	Low	Low	Serious	Low	Low	Serious
Csapo R., et al., 2019 [41]	Moderate	Moderate	Low	Low	Low	Low	Serious	Serious
Fischer F., et al., 2018 [42]	Moderate	Low	Low	Low	Low	Low	Low	Moderate
Han H.S., et al., 2008 [43]	Serious	Low	Low	Low	Critical	Low	Moderate	Critical
Guney-Deniz H., et al., 2020 [45]	Serious	Low	Low	Low	Low	Low	Low	Serious
Hunnicutt J.L., et al., 2019 [49]	Serious	Low	Low	Low	Low	Low	Moderate	Serious
Lee J.K., et al., 2016 [15]	Serious	Moderate	Low	Low	Low	Low	Moderate	Serious

D1, Bias due to confounding; D2, Bias in the selection of participants into the study; D3, Bias in the classification of interventions; D4, Bias due to deviations from intended; D5, Bias due to missing data; D6, Bias in the measurement of outcomes; D7, Bias in selection of the reported results. Background color caption: green = low risk of bias; yellow = moderate risk of bias; orange = serious risk of bias; and red = critical risk of bias.