Modification of additive effect between vitamins and ETS on childhood asthma risk according to GSTP1 polymorphism: A cross -sectional study

Abstract

Background: Asthma is characterized by airway inflammation, and bronchial airways are particularly susceptible to oxidant-induced tissue damage. Objective: To investigate the effect of dietary antioxidant intake and environmental tobacco smoke (ETS) on the risk of childhood asthma according to genotypes susceptible to airway diseases. Methods: This cross-sectional study included 1124 elementary school children aged 7-12 years old. Asthma symptoms and smoking history were measured using the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Intake of vitamin A (including retinol and β-carotene), C, and E was measured by a semi-quantitative food frequency questionnaire (FFQ). GSTP1 polymorphisms were genotyped from peripheral blood samples. Results: ETS was significantly associated with presence of asthma symptoms (adjusted odds ratio [aOR], 2.48; 95 % confidence interval [CI], 1.29-4.76) and diagnosis (aOR, 1.91; 95 % CI, 1.19-3.06). Dietary antioxidant intake was not associated with asthma symptoms, although ETS plus low vitamin A intake showed a significant positive association with asthma diagnosis (aOR, 2.23; 95 % CI, 1.10-4.54). Children with AA at nucleotide 1695 in GSTP1 who had been exposed to ETS and a low vitamin A intake have an increased risk of asthma diagnosis (aOR, 4.44; 95 % CI,1.58-12.52) compared with children who had not been exposed to the two risk factors. However, ETS exposure and low vitamin A intake did not significantly increase odds of asthma diagnosis in children with AG or GG genotypes. Conclusion: Low vitamin A intake and ETS exposure may increase oxidative stress and thereby risk for childhood asthma. These relationships may be modified by gene susceptibility alleles of GSTP1.