Risk factors for rhinitis, allergic conjunctivitis and eczema among schoolchildren in Uganda

Background: The prevalence of allergy-related diseases (ARDs), including rhinitis, allergic conjunctivitis and eczema, is on the increase in Africa and globally. The causes of this increase are not well established. Objectives: To investigate the risk factors for ARDs among schoolchildren in Uganda. Methods: We conducted a secondary data analysis of a large asthma case-control study involving 1,700 schoolchildren, 5-17 years, in urban Uganda. ARDs were defined according to the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Skin prick testing (SPT) was conducted using standard procedures and allergen-specific IgE (asIgE) using ImmunoCAP. We used inverse probability weighting to account for the differences in the sampling fractions in all our analyses. Results: The lifetime prevalence of reported rhinitis, allergic conjunctivitis and eczema was 43.3%, 39.5%, and 13.5%, respectively. There was overlap of ARDs, with 66.3% of 1,193 schoolchildren who reported having ever an ARDs (including asthma) reporting two or more. The important risk factors for rhinitis ever were city residence at birth [adjusted odds ratio (95% confidence interval) 1.97 (1.26-3.10) compared to rural]; fathers [2.08 (1.57-2.75)] and mothers history of allergic disease [2.29 (1.81-2.91)]; frequent de-worming in the last 12 months [1.80 (1.32-2.45), >2 versus none]; current high frequency of trucks passing on the street near home [1.90 (1.19-3.03), almost all the time versus rarely] and positive SPT [1.56 (1.24-1.96)] but not asIgE [1.33 (0.81-2.18)]. The same pattern of risk factors was observed for allergic conjunctivitis and eczema. Conclusion: We found extensive multi-morbidity of, and overlap in the risk factors for, rhinitis, conjunctivitis, and eczema - similar to asthma risk factors - among schoolchildren in urban Uganda. This suggests a similar underlying cause for all ARDs, associated with exposure to urban lifestyles and environment in Uganda. Thus, epidemiological research should investigate causes of all ARDs as one disease entity.