Effect of Childhood Asthma on T1DM
A total of 56 single nucleotide polymorphisms (SNPs) associated with childhood asthma were selected for genome-wide significance (threshold: P <5*10-8) from the hitherto largest asthma GWAS of UK Biobank (UKBB) (Table S1).13 These SNPs explained 8.68% of the variation in childhood asthma risk. The F statistic is 2,881, indicating that the instruments could strongly predict childhood asthma.14We performed linkage disequilibrium (LD)-clumping restricted to r2 < 0.01, Clumping distance > 5000kb and retained SNPs at a GWAS threshold of statistical significance to eliminate LD. When a particular SNP was not available in the outcome dataset, proxy SNPs were used instead through LD tagging (Rsq > 0.8). Then 30 SNPs were selected as IVs for MR analysis by removing the SNPs for lack of required information, being palindromic or incompatible alleles. Effect estimates of these childhood asthma-associated SNPs on the risk of T1DM were assessed using the summary statistics from the FinnGen datasets (2,636 T1DM cases and 8,2655 controls of European ancestry). Detailed description is provided on the FinnGen research project website (https://www.finngen.fi/en).