Table 2.

Quality assessment for included non-RCT studies

Author year	Li li 2021	Jie Zhang 2021	Nardin Aslih 2021	Yuanyuan Man, 2020	Jie Zhang 2019	Lee KH 2017	Jian Mei Yu 2015	Yan Jun Hu 2014
Representativeness of the exposed cohort	*	*	*	*	*	*	*	*
Selection of the non-exposed cohort	*	*	*	*	*	*	*	*
Ascertainment of exposure	*	*	*	*	*	*	*	*
Demonstration that outcome of interest was not present at start of study	/	/	/	/	/	/	/	/
Comparability of cohorts on the basis of the design or analysis	**	**	**	**	**	/	**	**
Assessment of outcome	*	*	*	*	*	*	*	*
Was follow-up long enough for outcomes to occur	*	*	*	*	*	*	*	*
Adequacy of follow-up of cohorts	*	*	*	*	*	*	*	*
Summary quality score	8	8	8	8	8	6	8	8