Statistical analysis
Meta-analysis was conducted using Stata software 16.0 (Stata, College
Station, TX, USA). The outcomes of the dichotomous variables, such as
odds ratio (OR) and hazard risk ratio, were included in this study. The
included effect estimates (OR, PR, RR and HR) were combined together in
subgroup analysis (16, 17). The I2 statistical test
was used to assess the heterogeneity of included studies. The findings
with p < 0.05 were statistically significant. When the
estimated effect was heterogeneous (I2>
50% or p <0.05), the random effect model was applied;
otherwise, the fixed effect model was applied. The sensitivity of each
study was assessed by omitting one study at one time to reduce
heterogeneity of the included studies. We did not assess publication
bias because less than ten studies were included (18).