3.4 Data analysis and synthesis
We used the Review Manager software (RevMan-5) to conduct our statistical analyses. The overall odds ratio (OR), and the 95% CI for each analyzed parameter were pooled using a fixed-effects model. Furthermore, we have drawn forest plots to evaluate the results of pooling visually. OR value >1 indicates an increased risk of complex POAF, OR value 1 indicates no observed association, and OR <1 indicates decreased risk of POAF. A two-sided P-value < 0.05 was considered statistically significant. Furthermore, the heterogeneity of the studies results was calculated using the Higgins I2 , which measures the percentage of the total variation across the included studies23 . The values of I2 lie between 0 and 100%. A value of 0% indicates no heterogeneity. We classified heterogeneity in mild (I2 < 25%), moderate (25≤ I2 <50%), severe (50≤ I2 <75%), and very severe (I2 ≥75%) 24 .