Table 2.

Newcastle–Ottawa score of the included studies

Study ID	Exposed cohort representative	Non-exposed cohort selected from same source	Exposure ascertained	Outcome of study was not present at start of the study	Comparability	Adequate assessment	Follow-up was long enough	Adequate follow-up	Quality score
Chen et al. [22]	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7
Wang et al. [15]	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7
Banerjee et al. [24]	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7
Cao et al. [23]	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7
Chen et al. [21]	Yes	Yes	Yes	Yes	1	Yes	Yes	Yes	8
Nikpouraghdam et al. [20]	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7
Ruan et al. [19]	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7
Shi et al. [17]	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7
Shi et al. [18]	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7
Wang et al. [16]	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7
Yan et al. [14]	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7
Zhou et al. 13	Yes	Yes	Yes	Yes	0	Yes	Yes	Yes	7