Sensitivity analysis
In UVMR analyses, in the causality of MA in relation to EA, AFS, and AFB, heterogeneity was found in the results of the Cochran Q-test. However, the results analysed by IVW MR along with the complementary methods: simple mode, weighted mode and weighted median, apart from MR–Egger, showed that EA, AFS, AFB all had statistically significant causal relationship with MA, which suggested that these associations were robust and plausible. Uncertainty existed about the causal relationship between CP and MA, as the results of this analysis were not confirmed by all complementary methods. The MR Egger intercepts indicate directional pleiotropy. In the MVMR analyses, using the primary method IVW and the complementary method Egger, the consistency of the results of both can confirm the inference of causality. In addition, there was no significant evidence for a nonzero intercept of multivariable MR Egger regression, which also supports the reliability of the results for multivariable MR analyses.