Table 2B. Newcastle-ottawa scale for assessment of quality of in included case-control studies.

Author	Quality assessment criteria								Overall Quality
	Selection				Comparability	Outcome
	Is the case definition adequate?	Representativeness of cases?	Selection of control?	Definition of control?	Study control for age/gender and additional factor?	Ascertainment of exposure?	Same method of cases/controls?	Non-response rate
Shin et al. 2015	*	*	-	*	*	*	*	-	6
Zamora-Ros 2013	*	*	-	*	**	*	*	-	7
Budhathoki et al. 2011	*	*	*	*	**	*	*	-	8
Rossi et al. 2010	*	*		*	**	*	*	*	8
Ward 2010	*	-	-	*	**	*	*	-	7
Kyle et al. 2009	*	*	*	*	**	*	*	*	9
Theodoratou et al. 2007	-	*	*	*	**	*	*	*	8
Cotterchio et al. 2006	*	*	-	*	*	*	*	*	7
Rossi et al. 2006	*	*	*	-	*	*	*	-	6

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