Fig. 4

Sensitivity analyses and publication bias assessed by Egger’s tests of seven included studies in this meta-analysis. Exclusion of a single study conducted in China changed the overall risk estimate obviously, with a lower OR of 0.80 (95% CI: 0.73–0.88, A). The Egger’s (P=0.565) and Begg’s (P= 0.368) tests confirmed no evidence of publication bias