Asthma in children: origins and outcomes

Abstract

Asthma is one of the most common chronic diseases in the world. At school age, 4-7% of all children is experiencing asthmatic symptoms. Improvement of asthma control and health related quality of life (HRQOL) may lower the huge burden of this disease. This requires insight into the determinants of asthma control and asthma related quality of life. Although it seems to be attractive to control all the determinants of asthma control in order to achieve proper asthma management, in clinical practice we do not succeed. In this thesis, we showed that in children, upper and lower respiratory tract infections are important determinants of asthma control. We also found that during the fall asthmatic children experience lower HRQOL. This may be due to the higher prevalence of viruses during this season. We furthermore identified two self perceived triggers for wheeze that negatively influenced HRQOL: emotions and perceived foods and drinks that trigger wheeze. In 91% of the children that perceived food and drinks to trigger wheeze, food allergic symptoms were present. It is not unlikely that underlying fear for food related respiratory symptoms may be present in this group of children. Besides the important role viruses play in asthma control, some viruses are thought to be associated with the development of asthma. For instance, Respiratory Syncytial Virus (RSV), which is the most frequent cause for hospitalization in infancy. It is unknown why RSV causes mild disease in some children, and severe disease, requiring hospitalization, in others. In most hospitalized no risk factors are present. We showed that hospitalization for RSV bronchiolitis during infancy is associated with increased risk of wheezing, asthma, and impaired lung function at age 6, as compared to an unselected birth cohort. We also studied whether early treatment of RSV bronchiolitis affects these long term outcomes, and showed that high dose inhaled beclomethasone during RSV bronchiolitis does not affect lung function, nor prevents the development the atopic diseases during long term follow-up. An explanation for this ineffectiveness may be the fact that these children are predisposed to develop asthma and already have lower lung functions from birth. We studied this hypothesis and found that neonatal lung functions in children that would be hospitalized for a severe RSV infection in the first year of life were significantly lower than children experiencing a less severe RSV infection.