The Epidemiology of Severe Childhood Asthma

Abstract

Severe asthma affects approximately 1 in 20 asthmatics, and the healthcare resources utilization and mortality are disproportionately high in these patients. Deaths from asthma are relatively rare and correlate poorly with prevalence, and many patients who die from asthma are classified as having a mild/moderate disease based upon their treatment requirements. One of the challenges to understanding the epidemiology, pathophysiology, and etiology of severe asthma is its heterogeneity. Reasons for poor symptom control among patients on maximum treatment range from the wrong diagnosis to nonadherence with prescribed treatments and genuinely therapy-resistant disease. Social and personal circumstances often determine that patients do not adhere to asthma treatments, and this presents to caregivers with uncontrolled asthma. Patients with severe asthma generally start to experience symptoms earlier than those with mild/moderate disease and have early development of atopy and a T2-like diathesis. Severe asthma is often associated with comorbid condition, including obesity, rhinitis, nasal polyps, food allergy, and vocal cord dysfunction. An important determinant of severe asthma is a predisposition to the development of severe exacerbations. Genetic factors and host innate immune responses to viruses may be important determinants of asthma severity and exacerbations. History of sinusitis and of gastroesophageal reflux is associated with proneness for exacerbations. Severe childhood asthma is associated with a loss of lung function during childhood and is a major determinant of early-onset COPD. Therefore, prevention of severe childhood asthma ought to be a major component of the efforts to decrease early mortality due to COPD.