According to GCTA, the heritability of AAB was moderate, but the estimate did not reach statistical significance (h2=0.25, s.e.=0.20, P=0.09). The GWAS results are summarized in a Manhattan plot in Figure 1 and the quantile–quantile plot is shown in Supplementary Figure S1. The genomic inflation factor was acceptable, λ=1.004, suggesting that technical issues and population stratification did not inflate the results. No single SNP met the strict genome-wide significance threshold (P⩽5 × 10−8). The most highly associated SNP was rs4728702 (P=5.8 × 10−7), located in the protein-coding gene adenosine triphosphate-binding cassette, sub-family B (MDR/TAP), member 1 (ABCB1) on chromosome 7. The top SNP results (P⩽5 × 10−6) from this analysis are summarized in Table 1.
