Table S1.

The Newcastle-Ottawa Scale (NOS) for assessing the quality of studies in the meta-analyses

Studies	Selection				Comparability	Exposure			Total quality score
Author, year	Is the case definition adequate?	Representativenessof the cases	Selection of controls	Definition of controls	Comparability of cases and controls	Ascertainment of exposure	Same method of ascertainment for cases and controls	Non-response rate
Nariman-Saleh-Fam et al, 201713	*	*		*	**	*	*		7
Bulibu et al, 201712	*	*	*	*	**	*	*		8
Shen et al, 201611	*	*		*	**	*	*		7
Zhu et al, 201510	*	*		*	**	*	*		7
Zhang et al, 20149	*	*	*	*	**	*	*		8
Wang et al, 20148	*	*	*	*	**	*	*		8
Qu et al, 20147	*	*	*	*	**	*	*		8
Wang et al, 20134	*	*	*	*	**	*	*		8
Wei et al, 20135	*	*		*	**	*	*		7
Yin et al, 20136	*	*		*	**	*	*		7
Umar et al, 20133	*	*		*	**	*	*		7
Guo et al, 20101	*	*		*	**	*	*		7
Wang et al, 20102	*	*		*	**	*	*		7