Table 1.

Newcastle-ottawa scale assessment for studies

Publication	Year	Newcastle-Ottawa Scale								Total
		Selection				Comparability	Outcome
		Representatives of exposed cohort	Selection of the non-exposed cohort	Ascertainment of exposure	Outcome demonstration at start		Assessment of outcome	Follow-up long enough for outcome to occur	Adequacy of follow-up
El-Azeem	2013	*	*	*	*	**	*	*	*	9
Hamaguchi	2007	*	*	*	*	**	*	*	*	9
Haring	2009	*	*	*	*	**	*	*	*	9
Hwang	2008	*	*	*	*	**	*	*	*	9
Lee	2006	*	*	*	*	**	*	*	*	9
Lu	2009	*	*	*	*	**	*	*	*	9
Ruttman	2005	*	*	*	*	**	*	*	*	9
Stepanova	2012	*	*	*	*	**	*	*	*	9
Yu	2008	*	*	*	*	**	*	*	*	9
Zheng	2018	*	*	*	*	**	*	*	*	9