Table 2A. Newcastle-Ottawa scale for assessment of quality of in included Cohort studies.

Author	Quality assessment criteria								Overall QualityScore(max = 9)
	Selection				Comparability	Outcome
	Representativeness of exposed cohort?	Selection of the non-exposed cohort?	Ascertainment of exposure?	Outcome of interest was not present at start of study?	Study control forage/gender and additional factor?	Assessment of outcome?	Was follow-up long enough for outcome to occur?	Adequacy of follow-up of cohorts?
Nimptsch et al. 2015	*	*	*	*	**	*	*	*	9
Simons et al. 2009	-	*	*	*	**	*	*	*	8
Yang et al. 2009	-	*	*	*	**	*	*	-	7
Wang et al. 2009	-	*	*	*	**	*	*	-	7
Akhter et al. 2008	*	*	*	*	*	*	*	*	8
Mursu et al. 2008	-	*	*	*	*	*	*	*	7
Butler et al. 2008	*	*	*	*	**	*	*	*	9
Oba et al. 2007	*	*	-	*	*	*	*	*	7
Knekt et al. 2002	*	*	-	*	*	*	*	-	6

Each asterisk represents if individual criterion within the subsection were fulfilled.