2.4 Quality Assessment and Sensitivity Analysis
The Newcastle–Ottawa scale was applied to evaluate the quality of the
included studies and their risk of bias, and all of them had
Newcastle–Ottawa scores between 7 and 8, which ensured that they all
had high quality. We also performed sensitivity analyses to assess the
robustness of the findings and investigated the heterogeneity of the
included studies, assessing the impact of each study on the pooled
results and treating a study as a causation of high heterogeneity if it
was excluded because of its significantly lower I2.