Table 3.

Quality assessment using Newcastle-Ottawa Scale for cohort studies^a

Study	Selection			Comparability		Outcome			Study score
	Representativeness of The exposed cohort	Selection of the non-Exposed cohort	Ascertainment of exposure	Demonstration that the outcome of interest was not present at start of the study	Comparability of Cohorts on the basis of design or analysis	Assessment of outcome	Was follow- up Long enough For the outcome to occur?	Adequacy of follow up of cohorts
Yoo, et al., 2019	*	*	*	*		*	*	*	7/9
Joshipura, et al. 2018	*	*	*			*	*	*	6/9
Oluwagbemigun, et al. 2015	*	*	*	*	*	*	*		7/9
Liljestrand, et al. 2015	*	*	*			*	*	*	6/9
Greenblatt, et al. 2016	*	*	*	*		*	*	*	7/9
Zhang, et al. 2021	*	*	*	*	*	*	*	*	8/9

^aStudy score less than 4 indicates low quality, a score of 4 to 6 represents poor to moderate, and a score 7 or higher indicates as a good quality