Table 2. Quality Assessment for Included Studies.

Study, Year	Selection					Comparability		Outcome					Total
	Representativeness of the sample		Non-exposed group from same community	Outcome of interest was not present at start of study	Validated measurement tool	Comparability of different samples on the basis of the design or analysis		Assessment of outcome		Adequate follow up	Completeness of follow up
	Truly representative	Somewhat representative				Study controls for important factor	Study controls for any additional factor	Independent blind assessment	Record linkage		Complete	Small number loss follow up
Yang 2007		*	*	*	*			*		*		*	7
Xie 2012		*	*	*	*			*		*		*	7
Wu 2011		*	*	*	*	*	*		*	*	*		9
Vogt 2014	*		*	*	*	*	*	*		*	*		9
Prasad 2013	*		*	*	*	*	*		*	*	*		9
Park 2010			*	*	*	*	*	*		*	*		8
Liao 2011		*	*	*	*	*	*	*		*	*		9
Johnson 2007	RCT (Low risk of selection, blinding, and reporting bias)