HLA-DRB1 and Obesity: Although there was proportion of nonresponders among the controls, this bias is probably modest because the prevalence of lifestyle factors, such as smoking and socioeconomic status, among controls was consistent with that of the general population.32 Subjects who were excluded due to unknown IM history did not differ with regard to obesity at age 20 years, EBNA-1 antibody levels, or DRB1*15:01 status compared with those with known IM history.