Table 2.

Newcastle-Ottawa Scale (NOS) score of included articles

Number	Author	Year	Selection				Comparability	Exposure			Total	Average
			Adequate definition	Representativeness	Selection of Controls	Definition of Controls		Ascertainment of exposure	Same method	Non-Response rate
1	Gao et al. [28]	2019	1	1	1	1	0	1	1	0	6	5.85
2	Hong et al. [29]	2017	1	1	1	1	0	1	1	0	6
3	Lee et al. [30]	2016	1	1	1	1	0	1	1	0	6
4	Loeffelholz et al. [31]	2017	1	0	1	1	0	1	1	0	5
5	Long et al. [32]	2019	1	1	1	1	0	1	1	0	6
6	Yang et al. [33]	2017	1	1	1	1	0	1	1	0	6
7	Zhang et al. [34]	2019	1	1	1	1	0	0	1	0	5
8	Zhang et al. [35]	2021	1	1	1	1	0	1	1	0	6
9	Zhu et al. [36]	2016	1	1	1	1	0	1	1	0	6
10	Altun et al. [37]	2018	1	1	1	1	0	1	1	0	6
11	Yang et al. [38]	2020	1	1	1	1	0	1	1	0	6
12	Ma et al. [39]	2019	1	1	1	1	0	1	1	0	6
13	Yilmaz et al. [40]	2009	1	1	1	1	0	1	1	0	6