Table 2.

Quality assessment scores for the included cross-sectional studies

Author	Representativeness of the sample	Sample size	Non-respondents	Ascertainment of the exposure	Comparability	Assessment of the outcome	Statistical test	Total
Huang et al.2	+	+	-	++	++	+	+	8
Guan et al.23	+	+	-	++	++	+	+	8
Fu et al.24	-	+	-	++	++	+	+	7
Zhou et al.25	+	+	-	++	++	+	+	8
Chen et al.26	+	+	-	++	N/A	+	+	6
Chen et al.27	+	+	-	++	++	+	+	8
Chen et al.28	+	+	-	++	++	+	+	8
Chen et al.29	+	+	-	++	++	+	+	8
Ai et al.30	+	+	-	++	++	+	+	8
Xu et al.31	+	+	-	++	++	+	+	8
Zhang et al.32	+	+	-	++	++	+	+	8
Zhao et al.5	-	+	-	++	++	+	+	7
Zhao et al.33	+	+	-	++	++	+	+	8
Tian et al.34	-	+	-	++	++	+	+	7
Wang et al.35	-	+	+	++	++	+	+	8
Wang et al.36	-	+	+	++	N/A	+	+	6
Huang et al.37	-	+	-	++	N/A	+	+	5
Zhang et al.38	-	+	+	++	N/A	+	+	6
Zhang et al.39	+	+	-	++	++	+	+	8
Zhang et al.40	+	+	-	++	N/A	+	+	6
Zhao et al.41	+	+	+	++	++	+	+	7
Tang et al.42	-	+	-	++	++	+	+	7
Tang et al.43	-	+	+	++	N/A	+	+	6
Liao et al.44	+	+	-	++	++	+	+	8
Qian et al.45	+	+	+	++	++	+	+	9
Qiu et al.46	+	+	+	++	++	+	+	9
Shi et al.47	-	+	-	++	++	+	+	7
Wan et al.48	-	+	+	++	++	+	+	8
Xu et al.49	-	+	-	++	N/A	+	+	5
Wu et al.50	+	+	-	++	++	+	+	8
Xie et al.51	+	+	-	++	++	+	+	8
Xu et al.52	+	+	-	++	++	+	+	8
Zhou et al.25	-	+	-	++	++	+	+	7
Zhou et al.53	-	+	-	++	++	+	+	7
Cai et al.54	+	+	-	++	++	+	+	8
Feng et al.17	+	+	-	++	++	+	+	8
Feng et al.55	+	+	-	++	++	+	+	8
Fu et al.18	+	+	-	++	++	+	+	8
Ji et al.56	+	+	-	++	++	+	+	8
Han et al.57	-	+	-	++	++	+	+	7
Jiang et al.58	-	+	-	++	++	+	+	7
Yang et al.59	-	+	-	++	++	++	+	8

N/A: Not applicable