Allergic Rhinitis in Childhood and Young Adulthood: Epidemiology, Prevalence and Risk Factors

Abstract

Background and Aim: Allergic rhinitis (AR) is a common chronic condition among young people. This thesis examines the prevalence, risk, and protective factors of AR in 12-year-olds. It also compares questionnaire-derived AR data with Swedish national registers. It analyses AR trends, exploring AR risk factors in young adults. Finally, it examines the incidence and remission of AR from childhood into young adulthood and identifies associated risk factors. Methods: Data for the first two papers were derived from a longitudinal cohort of children born in 2003 in Western Sweden. Parents completed questionnaires for their children from 6 months to 12 years (76% response rate at 12 years). Personal identification numbers linked 3,634 children to Swedish national registers. Paper III presents a cross-sectional analysis of 16- to 25-year-olds from the West Sweden Asthma Study; 2,143 participants in 2008 and 2,484 in 2016. Paper IV included children in grades 1-2 in Norrbotten, using a questionnaire and skin prick tests (SPTs) in 2006 (8-year-olds) and 2016-2017 (19-year-olds). In total, 2,250 participants (91% participation rate) completed the questionnaire; 1,338 underwent SPTs at 8 and 19 years of age. Results: At age 12 years, 22% reported AR. Risk factors were parental AR, male sex, food allergy, and eczema at the first year of life, while living on a farm and early fish consumption at least once a month were protective factors. Concordance between questionnaires and registers on AR was weak due to insufficient registry data on over-the-counter medication and primary care. From 2008-2016, AR prevalence remained stable (22.5% to 24.4%, p=0.144). Growing up on a farm reduced AR risk in both 2008 and 2016. AR incidence from ages 8 to 19 years was 33.6% and the remission rate 40%. Sensitisation increased the risk of AR incidence and reduced the odds of remission. Conclusion: AR affects >20% of children at the age of 12 years. Genetic predisposition and environmental exposures play an important role in AR development, with protective factors such as farm living and early fish consumption suggesting potential preventive strategies. Sensitisation significantly impacts AR, indicating the need for early identification of individuals at risk. Integrating reliable parental questionnaires and registry data provides invaluable tools for sustained AR research.