APLN and angina pectoris: As two studies involved controls with atrial fibrillation [13] and stable angina [21], respectively, a sensitivity analysis by excluding the two studies found the reduction in circulating apelin concentration was still significant (WMD: -1.465 ng/mL, 95% CI: -2.024 to -0.906, P < 0001), with significant heterogeneity (I2: 99.3%, P < 0.001).