Both severity and triggers of preschool wheeze increase the risk of asthma at school age

Background: Multiple trigger wheeze (MTW) has been suggested to predict later asthma, but might rather be a marker of severity of wheeze and that it is the severity that defines future risk of asthma. Our aim was to compare severity and triggers of preschool wheeze as predictors of asthma at 8 years. Methods: Data were obtained from the 4- and 8-year follow-ups of 3753 children in a longitudinal birth cohort study. Asthma severity (mild, moderate or severe) at age 4 was based on doctor diagnose of asthma, frequency of wheeze during the past 12 months and treatment with inhaled corticosteroids. Triggers were defined as episodic viral wheeze (EVW) or MTW. Results: Severe wheeze and MTW both independently increased the risk of doctor-diagnosed asthma at 8 years. Severity had the largest impact. At each step of severity, MTW potentiated the risk of asthma compared to having EVW, see Figure. Children with severe wheeze and MTW at preschool age had the greatest risk of doctor-diagnosed asthma at 8 years, adjusted OR 133.6 (95% CI 62.6-285.4). However, also the children with severe EVW at preschool age had an increased risk of asthma at 8 years, aOR 120.9 (50.7-288.4). No significant interaction was seen between trigger factor and severity (p=0.207). Conclusion: Severity of wheeze increased the risk of doctor-diagnosed asthma at 8 years. However, at each level of severity, MTW potentiated the risk of asthma compared to having EVW.