This SNP, along with SNPs rs6910071 and rs660895, is a tag SNP for the HLA-DRB1*0401 allele.
The HLA-DRB1*0401 allele has been associated with higher risk for rheumatoid arthritis, and in particular, rheumatoid vasculitis. The association is seen particularly for individuals carrying two copies of, i.e. homozygous for, the allele. The reported odds ratio for rs3817964(T;T) homozygotes is 6.2 (CI: 1.01 - 37.9). [PMID 15529352]
The risk for rheumatoid arthritis may be higher for individuals carrying one copy (one "dose") of the HLA-DRB1*0401 allele, if they also carry a different HLA-DRB1 risk allele. In particular, *0401/*0404 individuals are reported to have an odds ratio for rheumatoid vasculitis of 4.1 (CI: 1.1 - 16.2), and *0401/*0101 individuals have an odds ratio of 4.0 (CI: 1.4 - 11.6). [PMID 15529352]