Table 2.

Quality assessment using New Castel Ottawa Scale.

Authors/reference	Selection				Comparability	Outcomes			Total Score
	Representative of Exposed Cohort	Selection of Non-Exposed Cohort	Ascertainment of Exposure	Outcomes not Present at Baseline		Assessment of Outcomes	Sufficient Follow up Duration	Adequate Follow up
Bruce et al.	1	0	1	1	2	1	1	1	8
Wu et al.	1	0	1	1	1	1	1	1	7
Poovorawan et al.	1	0	1	1	2	1	1	1	8
Al-Ghamdi et al.	1	0	1	1	1	1	1	1	7
Su et al.	1	0	1	1	1	1	1	1	7
Al Faleh et al.	1	0	1	1	1	1	1	1	7
Spada et al.	1	0	1	1	2	1	1	1	8
Middleman et al.	1	0	1	1	2	1	1	1	8
Avidoca et al.	1	0	1	1	2	1	1	1	8
Gold et al.	1	0	1	1	2	1	1	1	8
Tsega et al.	1	0	1	1	1	1	1	1	7
Amini et al.	1	0	1	1	1	1	1	1	7