S2.

Methodological characteristics of included studies and quality score

No.	Authors	Year	Representativ-eness of population	Non exposed cohort	Ascertainment of exposure	Outcome not present at start of study	Appropriate confounding measurement and account	Sufficient measurement of outcomes	Complete-ness of follow-up
1	Lin et al.	2015	0	1	1	1	2	2	2
2	Tang et al.	2015	0	1	1	1	2	1	2
3	Meniawy et al.	2016	0	1	1	1	1	1	2
4	Sorensen et al.	2016	0	1	1	1	1	1	2
5	Cho et al.	2017	0	1	1	1	2	2	2
6	Kobayashi et al.	2018	0	1	1	1	2	1	2