Figure 5. Begg's Funnel Plot* for visual assessment of the presence of publication bias for all studies included in the meta-analysis (each study is represented by an open circle).

*Tests for Publication Bias. For Prospective Cohort Studies (n = 9), Egger's bias 2.50 (p 0.011). For Cross-Sectional Studies (n = 13), Egger's bias 2.64 (p<0.001). Overall Egger's bias p<0.001.