KCNQ1 and obesity due to melanocortin 4 receptor deficiency: With regards to limitations, in the present study, the effects of multiple covariates on QTc, including NOS1AP genotype, KCNQ1 genotype, sex, and age were assessed in the pedigree-based measured genotype association analysis, however, as the study population is relatively young (mean age 31 ± 22 years) and otherwise healthy, the model did not include additional covariates, such as obesity or drug use (medical or other), which may influence QTc.