Table 3.

Quality assessment using the Newcastle–Ottawa quality assessment scale for each non-randomized controlled trial

Variable	Lan et al. [7]	Vaishnav et al. [8]	Wei et al. [11]	He et al. [16]	Noh et al. [17]	Lee et al. [18]	Son et al. [19]	Wang et al. [21]	Wang et al. [23]	Yan et al. [24]	Li et al. [25]	Shao et al. [27]	Yi et al. [28]	Wang et al. [29]	Sun et al. [31]	Hu et al. [32]	Sha et al. [33]	Chang et al. [9]	Ruan et al. [34]	Zhu et al. [35]	Zhang et al. [36]	Gou et al. [10]	Luo et al. [37]
Selection
Representativeness of exposed cohort	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1
Selection of non-exposed cohort	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1
Ascertainment of exposure	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1
Demonstration that outcome of interest was not present at start of study		1	1	1								1	1							1
Comparability
Study controlled for age or gender	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1
Study controlled for any additional factor	1	1	1	1	1	1	1	1	1	1	1	1	1		1	1		1	1	1	1	1	1
Outcome
Assessment of outcome	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1
Follow-up long enough for outcomes to occur	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1
Adequacy of follow-up of cohort	1		1				1	1	1	1	1	1	1		1	1	1	1	1	1	1	1	1
Total	8	8	9	8	7	7	8	8	8	8	8	9	9	6	8	8	7	8	8	9	8	8	8