Genetic, familial and environmental correlates of asthma among early adolescents in Sri Lanka: a case control study

Despite advances in management, the mortality and morbidity due to asthma are increasing globally. Identification of specific correlates in the local context is useful in disease management. The objective of this study was to estimate the prevalence and to describe selected correlates of asthma among12-14 year old school children in a district in Sri Lanka. A school based cross-sectional study was conducted using a self administered questionnaire. Multi-staged stratified cluster sampling was used to select 42 classes in grades 7, 8 and 9. "Current asthma" (CA)(case) was defined as 'having Physician Diagnosed Asthma (PDA) and having had wheezing during the previous 12 months'. For each case, two healthy controls were selected from the same class to assess correlates. Information on correlates was collected by trained field midwives during home visits. Backward stepwise logistic regression model was used for analysis of correlates. Skin Prick Testing was carried out among asthmatics together with their healthy siblings using standard extracts of House Dust Mite (HDM), cockroach and Blomia. Ethical clearance was obtained from Ethical Review Committee, Faculty of Medicine, Colombo. Out of 1483 subjects participated, 753 were females (50.8%). The prevalence rates for current wheezing (CW), ever wheezing (EW), current asthma (CA), and physician diagnosed asthma (PDA) were 16.7%, 19.4%, 10.7% and 14.5% respectively. A total of 158 CA cases were identified. Information on correlates of asthma was collected for 145 CA cases (97.9%) and for 285 controls (96.6%). The unconfounded predictors of having CA among adolescents in the present sample were; only child in the family (OR = 4.2, 95% CI: 1.7-9.9); first born of the family (OR = 2.6 95% CI: 1.3-5.2); presence of allergic rhinitis (OR = 2.7, 95% CI: 1.6-4.6); family history of asthma (OR = 1.8, 95% CI: 1.1-3.2); family history of allergic rhinitis (OR = 1.9, 95% CI: 1.1-3.2); family history of eczema (OR = 1.8, 95% CI: 1.0-3.2). Higher risk of sensitization to cockroach, HDM and Blomia was seen among asthmatics compared to healthy siblings. A significant proportion of students reported to have asthma. Atopy and other genetic and environmental correlates should be considered as important correlates in asthma management among early adolescents in Sri Lanka.