Characterization of wheezing phenotypes in the first 10 years of life

Background Childhood wheezing illnesses are characterized into different phenotypes. However, severity of the disease associated with these phenotypes has not been extensively studied. Objectives To determine characteristics of childhood wheezing phenotypes in the first decade of life using health outcomes plus measurements of atopy, lung function and bronchial hyper-responsiveness. Methods A whole population birth cohort (n = 1456) was prospectively studied to examine the natural history of childhood wheezing. Children were seen at 1, 2, 4 and 10 years for questionnaire completion and prospectively collected data used to define wheezing phenotypes. Assessment was made of adverse health outcomes plus spirometry, bronchial hyper-responsiveness, serum IgE measurement at 10 years and skin test sensitization at both 4 and 10 years for wheezing phenotypes. Results Phenotypic analysis identified that 37% early life wheezers (symptom onset by age 4 years) still wheezed at 10 years. These persistent wheezers showed significantly more physician-diagnosed asthma in early life (P < 0.005 at 2 years) than early transient wheezers (wheezing transiently with onset by age 4 years). Overall they experienced greater multiple hospital admissions (P = 0.024), specialist referral (P = 0.009) and use of inhaled (P < 0.001) and oral steroids (P < 0.001) than early transient wheezers. They also demonstrated enhanced bronchial hyper-responsiveness compared with early transient wheezers (P < 0.001). However, both groups of early life wheezers showed impairment of baseline lung function at 10 years in comparison with non-wheezers: FEV1 (P < 0.029) and FEV1 /FVC ratio (P < 0.001) with persistent wheeze and PEF (P = 0.036) with early transient wheeze. Late-onset wheezers (onset from 5 years onwards) had similar BHR to persistent wheezers but maintained normal lung function at age 10 and had lower cumulative prevalence of adverse health outcomes than persistent wheezers. Conclusions Persistent wheezing with early childhood onset is associated with substantial morbidity in the first decade of life in association with high levels of atopy, bronchial hyper-responsiveness and impaired lung function at 10 years of age. Late-onset wheezing in the first decade of life could harbour potential for similarly significant disease subsequently.