3.5 | Publication bias and heterogeneity
We used the Deeks plot asymmetry test to examine publication bias. The funnel plot did not reveal significant publication bias (p=0.37) (Supplementary Figure 4 ). Heterogeneity among the included studies was measured using the Cochran-Q method and I2. Substantial heterogeneity existed among the studies (overall I2 for bivariate model 99.95%, 95% CI 94 to 100). The proportion of heterogeneity likely due to the threshold effect was small (p<0.05).