2.2.3 SNP Selection
We screened SNPs that had a strong connection with exposure factors
(P < 5×10-8) from the GWAS data of
exposure. We eliminated linkage disequilibrium (LD) between SNPs using a
clustering process (R2 < 0.001 and clumping
distance = 10, 000 kb) and SNPs having a minor frequency of alleles were
removed (MAF < 0.01) to ensure the results were practicable
and undisturbed. The SNPs we selected in exposure GWAS were matched with
the GWAS data of outcomes. If SNPs cannot be found in the GWAS data of
outcomes, the proxy SNPs with significant LD (r2> 0.8) were employed. Finally, once the palindrome SNPs
were excluded, the rest of the SNPs were chosen as IVs.