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).