Asthma control is considered the major goal of asthma management, while many determinants of control are difficult to modify. We studied the association between respiratory infection episodes (RTIs) of various types and asthma control.

Cross-sectional data were used from children aged 4–18 years with physician-diagnosed asthma who participated in a web-based electronic portal for children with asthma, allergies or infections. Asthma control was measured using the Childhood Asthma Control Test (C-ACT) or the Asthma Control Test (ACT). Linear regression was used to analyse the association between categories of numbers of various types of RTIs sustained in the preceding 12 months (categorized) and asthma control, adjusted for potential confounders.

Asthma control was assessed in 654 children, and 68.5% were clinically well controlled (ACT ≥ 20). Higher total numbers of RTIs in the last 12 months were strongly associated with a lower level of asthma control (p_trend < 0.001). Similarly strong statistically significant associations were found for subtypes of RTI: ≥4 vs. 0 otitis episodes: coefficient −1.7 (95% CI −3.3 to −0.2); ≥5 vs.0 colds: coefficient −2.3 (95% CI −3.0 to −1.6); ≥3 vs. 0 bronchitis episodes: coefficient −3.1 (95% CI −4.0 to −2.3), each with p_trend < 0.05.

Higher numbers of reported respiratory tract infections are associated with lower level of asthma control. The different type of respiratory tract infections contribute equally to less controlled asthma.