Burden of preschool wheeze and progression to asthma in the UK: Population-based cohort 2007 to 2017

Background: Wheeze is one of the most common symptoms of preschool children (age 1-5 years), yet we have little understanding of the burden in the United Kingdom. Objectives: We sought to determine prevalence and pattern of physician-confirmed preschool wheeze, related health care utilization, and factors associated with progression to school-age asthma. Methods: We used nationally representative primary and secondary care electronic medical records between 2007 and 2017 to identify preschool children with wheeze. Factors associated with asthma progression were identified in a nested cohort of children with follow-up from age 1 to 2 years, until at least age 8 years. Results: From 1,021,624 preschool children, 69,261 were identified with wheeze. Prevalence of preschool wheeze was 7.7% in 2017. Wheeze events were lowest in August and highest in late-autumn/early-winter. During median follow-up of 2 years (interquartile range, 1.2-4.0 years), 15.8% attended an emergency department, and 13.9% had a hospital admission, for a respiratory disorder. The nested cohort with prolonged follow-up identified 15,085 children; 35.5% progressed to asthma between age 5 and 8 years. Of children with preschool wheeze, without an asthma diagnosis, 34.9% were prescribed inhaled corticosteroids and 15.6% oral corticosteroids. The factors most strongly associated with progression to asthma were wheeze frequency and severity, atopy, prematurity, maternal asthma severity, and first reported wheeze event occurring in September. Conclusions: Preschool wheeze causes considerable health care burden, and a large number of children are prescribed asthma medication and have unplanned secondary care visits. Multiple factors influence progression to asthma, including first wheeze event occurring in September. (J Allergy Clin Immunol 2021;147:1949-58.)