The association between asthma and functional abdominal pain disorders in paediatric population: common pathophysiological mechanisms causing this association

Abstract

Asthma and functional abdominal pain disorders (FAPDs) are common paediatric disorders affecting quality of life. Though the association of asthma with irritable bowel syndrome has been reported, association with other FAPDs and possible underlying pathophysiological mechanisms have not been well described. This thesis describes the association between asthma and FAPDs (Phase I) and investigation of a possible pathophysiological mechanism using gastric motility and lung function tests (Phase II) in a cohort of children. In phase I, a cross-sectional survey was conducted among randomly selected adolescents. The validated Rome HI, and International Study on Asthma and Allergies in Childhood (ISAAC) questionnaires were utilized to identify adolescents with FAPDs and asthma respectively. Health-related quality of life (HRQoL) was evaluated using the Paediatric Quality of Life Inventory. Logistic regression showed independent association between asthma and functional abdominal pain [odds ratio (OR) 3.1, 95% confidence interval (CI) 1.6-6.0], functional dyspepsia (OR 3.9, 95% CI 1.1-13.5) and abdominal migraine (OR 10.2, 95% CI 2.6-39.5). HRQoL was significantly impaired among adolescents with both disorders. In phase II, an extensive review identified shared pathophysiological mechanisms; smooth muscle dysfunction, immune dysfunction, hypersensitivity, mucosal inflammation and barrier dysfunction, followed by a laboratory-based study involving 100 children (age 7-12 years), recruited into 4 groups of 25 each; asthma only, FAPDs only, asthma and FAPDs, and healthy controls. Asthma was diagnosed using clinical history and spirometry, and FAPDs by Rome III criteria. All subjects underwent real-time ultrasonography and spirometry. Gastric emptying rate, amplitude of antral contractions and antral motility index were significantly impaired in children with either disorder or both compared to controls (p<0.05). Antral motility index correlated with FEVi/FVC ratio (r=0.60, p=0.002) and FEF25%-75% (r=0.49,p=0.01) in children with both disorders. In conclusion, a strong independent association was noted between asthma and FAPDs. Gastric motility was significantly impaired in children with either disorder or both. Motility index measuring overall gastric motor function, shov/ed significant positive correlation with lung function parameters that measured airflow limitation. Primary disturbance of smooth muscle activity in airways and the gastrointestinal wall could be a possible pathophysiological mechanism for this association between asthma and FAPDs.