Allergic sensitization has a different impact on rhinitis in children living in differently polluted areas

Background: Environmental and host risk factors may play a different role on rhinitis. Aim of the study was to evaluate the possible changes in the role of allergic sensitisation as determinant of rhinitis in schoolchildren living in differently polluted areas. Method: Between March and December 2012 we evaluated 1325 schoolchildren (669 M), aged 10-16 years, selected from all the junior high schools of Gela (GE, 77 000 inhabitants/660 evaluated subjects), Mediterranean area of Southern Italy, close to a petrochemical complex, and those of Niscemi (NI, 26 400/355), Mazzarino (MA, 11 800/186), and Butera (BU, 4900/124), in rural areas respectively 15, 27, and 16 km far from GE. Parents of all children fulfilled a respiratory questionnaire and 1157 (87.3%) questionnaires were returned for evaluation. Rhinitis in the last 12 months (R) was defined as a positive answer to the question 'Have you ever had a problem with sneezing, or runny, or blocked nose apart from common cold or flu in the last 12 months?'. For a special indoor air quality study, we selected 109 subjects from GE and 111 children from BU, MA, and NI: within each subgroup, one half of subjects were selected among those reporting allergic respiratory symptoms (54 in GE, 56 in BU + MA + NI), while the remaining subjects were asymptomatic. Children underwent skin prick tests (SPT) for common aeroallergens. Allergic sensitisation was defined as the presence of at least one positive SPT. Results: In the overall sample (N = 1157) R was reported by 23.6%. Among selected children, R was reported by 33.9% in GE and 35.1% in BU + MA + NI (P = 0.85). Allergic sensitisation was present in 43.5% in GE and in 43.6% in BU + MA + NI (P = 0.99). In multiple logistic regression models evaluated separately for the polluted and the rural areas we found that, when corrected for confounding factors, allergic sensitisation was a significant risk factor for R only in BU + MA + NI (OR 6.2, IC 2.4-16.0, P = 0.0002) (OR in GE: 1.8, IC 0.7-4.8, P = 0.23). Conclusion: We suggest that in highly polluted urban areas the role of allergic sensitisation as risk factor for developing R is diminished. Local environmental factors deserve a thorough investigation. Funded by Operational Cross-Border Program Italy-Malta 2007-2013.