INTRODUCTION
Allergic rhinitis (AR) is an immunoglobulin E (IgE)-mediated inflammatory condition, which occurs in the nose with symptoms, such as nasal obstruction, watery rhinorrhea, itching, and sneezing. Following a global trend, in Korea, the prevalence of AR among children, adults, and the elderly has also increased rapidly over the past few decades.1-3 Various environmental factors, such as indoor allergens, air pollution, exposure to certain drugs during pregnancy, and factors affecting the microbiome based on hygiene hypotheses have been mentioned as the causes of increase in AR.4-7
The number of siblings may affect the development of hay fever and eczema, which suggests that changes in hygienic environmental factors during early childhood may cause an increase in allergic diseases.4,6-10In the past few decades, in Korea, hygienic environmental factors have drastically changed due to rapid westernization and industrialization, and children have been exposed to various environments.7,11Therefore, it is appropriate to explain the development of allergic diseases as a result of the combined effects of various environmental factors, rather than one environmental factor.
Recently, attempts to identify the association between genetic factors and prevalence of AR have increased. In recent studies, the A allele of interleukin-13 (IL-13) single nucleotide polymorphism, rs20541, is associated with the risk of AR in Asians.1,12Additionally, we previously reported the association between AR and Toll-like receptor 4 (TLR4) (rs1927911)/cluster of differentiation 14 (CD14) (rs2569190), which are receptors that enable response to microbes or cause tissue damage.13,14Glutathione S-transferase P1 (GSTP1) (rs1695) modulates the effect of environment-induced respiratory symptoms in children.15,16Studies on various genes have revealed the possibility that the development of AR is affected by multiple genes.1,13,17,18However, there are few studies on the combined effect of multiple genes on the development of AR.
Studies on environmental risk score (ERS) have been initiated to identify the effect of various environmental factors on the risk of developing chronic diseases, such as cardiovascular disease and diabetes mellitus.19,20The concept of polygenic risk score (PRS) is based on the assumption that even though a single genetic variant has an insignificant effect on the development of chronic disease, a combination of multiple genetic variants may exert a polygenic effect that increases disease risk, including allergic diseases.18,21,22
However, there are no studies on gene-environment interactions using ERS and PRS in children with AR. Therefore, we investigated the combined effect of early life hygienic ERS and PRS on the development of AR in school-age children.