An OR of 1.15 implies a variant frequency in the cases of 50.5%, based on 47% risk allele frequency in controls
(Solve: (n / (1 – n)) / (0.47 / 0.53) = 1.15)
According to http://www.cdc.gov/diabetes/news/docs/lifetime.htm the lifetime risk of type 2 diabetes is around 36% (averaging risk of males and females). Using this and mock case/control numbers based on the above we used the PGP calculator (counting chromosomes) to estimate absolute increased risk (absolute quantities only affect p-values, not attributable risk calculation). Note that this is an estimate based on per chromosome analysis rather than per individual analysis.
Note that this nonreference allele is the protective allele, the reference allele is the risk allele, so to mock these numbers we use the reverse: case+: 495, case-: 505, cont+: 530, cont-: 470. This estimates the risk of any given chromosome with this variant to have a lifetime risk of type 2 diabetes is 34.44% — an attributable decreased risk of 1.56%.