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

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.