Table 2. Bias analysis.

Author	Best et al. (2021) (22)	Burke et al. (2021) (24)	Can et al. (2021) (25)	Çayan et al. (2020) (27)	Erbay et al. (2021) (32)	Guo et al. (2021) (37)	Holtmann et al. (2020) (38)	Kadihasanoglu et al. (2021) (39)	Kaya et al. (2021) (40)	Ma et al. (2021) (49)
Selection
1	1	1	0	1	1	1	1	1	1	1
2	1	0	0	0	1	0	1	1	0	0
3	1	1	1	1	1	1	1	1	1	1
4	0	0	1	0	1	0	0	0	0	1
Comparability
1	1	0	0	0	1	0	1	1	0	0
Outcome
1	1	0	1	1	1	0	1	1	1	1
2	1	0	1	0	1	1	0	0	1	1
3	1	0	1	1	1	1	1	1	1	1
Total	7	2	5	4	8	4	6	6	5	6

Cohort – Newcastle-Ottawa Scale

More information see APPENDIX 1