ADRB2 and asthma: It has been reported that there are ethnic variations in the prevalence of these two β2-AR SNPs.[5, 6] Reports have indicated that these polymorphisms, which cause downregulation of the β2-AR, play a significant role in bronchial asthma since they are linked with functional changes in the β2-AR in the respiratory system.[6, 7] A study by Reihsaus et al. and other studies found no difference in allele frequency of these two polymorphisms in patients with and without asthma.[2, 8, 9]