Onset and persistence of respiratory/allergic symptoms in preschoolers: new insights from the PARIS birth cohort

Background The natural course of childhood asthma and allergy is complex and not fully understood. We aimed to identify phenotypes based upon the time course of respiratory/allergic symptoms throughout preschool years. Methods As part of the PARIS cohort, symptoms of wheezing, dry night cough, rhinitis and dermatitis were collected annually from birth to age 4 years. K‐means clustering was used to group into phenotypes children with similar symptoms trajectories over the study period. Associations of phenotypes with IgE sensitization and risk factors were studied using multinomial logistic regression. Results Besides a group with low prevalence of symptoms considered as reference (n = 1236, 49.0%), four distinct respiratory/allergic phenotypes were identified: two transient [transient rhinitis phenotype (n = 295, 11.7%), transient wheeze phenotype (n = 399, 15.8%)], without any relation with IgE sensitization, and two persistent [cough/rhinitis phenotype (n = 284, 11.3%), dermatitis phenotype (n = 308, 12.2%)], associated with IgE sensitization. Transient rhinitis phenotype was only associated with tobacco smoke exposure, which could irritate the airways. Transient wheeze phenotype was related to male sex and contact with other children (older siblings, day care attendance). Lastly, risk factors for both IgE‐associated phenotypes encompassed parental history of allergy, potential exposure to allergens and stress, known to be associated with the development of allergic diseases. Conclusion This study provides evidence for the existence of different respiratory/allergic phenotypes before school age. The fact that they differ in terms of sensitization and risk factors reinforces the plausibility of distinct phenotypes, potentially linked to irritation and infections for the transient phenotypes and to allergy for the persistent phenotypes.