Figure 2. Risk of All-Cause Mortality Between SVR And non-SVR.

The heterogeneity of the studies was tested using χ² test and I² statistic. If a significant heterogeneity (χ² test, P < 0.10) was found, the random-effect model was used in the analysis, and if the heterogeneity was not significant (χ² test, P ≥ 0.10), the fixed-effect model was used. Studies with substantial heterogeneity (I² ≥ 50%) are not suitable for meta-analysis.