Early life respiratory tract infections and risk of asthma

Abstract

Asthma is the most common chronic disease in children. Although early life wheezing illnesses have been suggested to play a role in the development of asthma, the influence of early childhood respiratory infections in the development of asthma is unknown. This dissertation investigates the associations between acute respiratory infections in early childhood and the risk of asthma.

In the prospective birth-cohort study called the Steps to the Healthy Development and Well-Being of Children (STEPS) Study, 923 Finnish children were followed intensively for upper and lower acute respiratory infections and the development of asthma from birth to 7 years of age. Nasal swab samples for respiratory viruses were obtained at the onset of respiratory symptoms during the first years of life. Asthma diagnoses were retrieved from medical records. Genome-wide genotyping was performed. In Study II, data from two prospective cohort studies of severe wheezing illnesses were included (n = 223).

Frequent acute respiratory infections in early childhood were associated with a higher rate of subsequent asthma. Recurrent wheezing illnesses, hospitalization for wheezing, and wheezing caused by either rhinoviruses or RSV in the first years of life were associated with an increased risk of asthma. Furthermore, both rhinovirus species A and C induced early wheezing illnesses were associated with a higher risk of asthma. Asthma risk alleles were associated with an increased risk of acute respiratory infections and viral wheezing illnesses during the first years of life.

These results contribute to the understanding of asthma pathogenesis and suggest that susceptibility to ARIs and asthma may share risk factors, or that recurrent ARIs in early childhood may predispose a child to the development of asthma. Future research should focus on interventions to modify infection-related asthma risk and the interaction between genetic and environmental asthma risk factors.