During the first 3 decades of life, rates of allergic sensitization and hay fever increased, whereas rates of asthma fell, according to a longitudinal birth cohort study published in the Journal of Asthma and Allergy. The relationship between allergic sensitization/hay fever and asthma appeared to grow stronger with age.
Atopy is often associated with asthma in children, and its prevalence in these children ranges from 40% to 77% compared with 21% to 64% in children without asthma. Atopic disorders such as eczema and allergic rhinitis often occur in children with asthma.
To determine how the rates of asthma, allergy, eczema, and hay fever vary over time and how these disorders relate to each other, researchers conducted a prospective study based on a longitudinal birth cohort of 253 participants. They conducted respiratory and immunological assessments when the participants were 1, 6, 11, 18, and 24 years of age.
The prevalence of allergic sensitization increased from 19% at age 1 year to 71% at age 24 years. However, the asthma rate dropped from 25% at 6 years of age to 11% to 15% between 11 and 24 years of age. In contrast, the allergic sensitization in participants with asthma doubled from 50% at age 6 years to 100% at age 24 years. The prevalence of hay fever rose throughout childhood from 7% at 6 years to 44% at 24 years of age, whereas eczema decreased from 25% at 6 years to 16% at 24 years.
Heredity played a role as well. In participants whose parents had atopy, the odds of having asthma were more than doubled (odds ratio, 2.63; P =.029), whereas 74% of those with asthma also had hay fever by age 24 years. In contrast, the relationship between eczema and asthma demonstrated significance only up to age 11 years, and the relationship between hay fever and asthma grew stronger in adolescence and early adulthood.
The authors noted a key limitation of this study: the definition of asthma was based on a physician’s diagnosis. It did not account for different asthma phenotypes or their underlying pathophysiology.
“Universal assumptions should not be made regarding the relationship between atopic disorders as they may be age dependent,” the researchers concluded.
Owens L, Laing IA, Zhang G, Tuner S, Le Souëf PN. Prevalence of allergic sensitization, hay fever, eczema, and asthma in a longitudinal birth cohort. J Asthma Allergy. 2018;11:173-180.