Objective: The association between the interleukin 4 (IL-4) gene -33C/T polymorphism and asthma risk is a subject of debate. We conducted a meta-analysis to evaluate the association between this polymorphism and asthma susceptibility.

Materials and Methods: A systematic search of electronic databases (Pubmed, EMBASE, Wanfang, China National Knowledge Infrastructure, and Weipu) was performed, and 18 studies involving 5523 cases and 5618 controls were identified. ORs with 95% CIs were used to assess the strength of association.

Results: A significant association between the -33C/T polymorphism and asthma susceptibility was observed for TT vs CT + CC (OR, 1.16; 95% CI, 1.05-1.28; P=.005). In the subgroup analysis by race, a significant association was found among whites (OR, 1.71; 95% CI, 1.14-2.57; P=.01) and Asians (OR, 1.14; 95% CI, 1.01-1.28; P=.04) but not among African Americans. In the subgroup analysis by atopic status, no significant association was found among atopic asthma patients (OR, 1.05; 95% CI, 0.89-1.24; P=.54) or nonatopic asthma patients (OR, 1.16; 95% CI, 0.81-1.67; P=.42). In the age-stratified analysis, an increased asthma risk was found in children (OR, 1.28; 95% CI, 1.01-1.63; P=.04) but not in adults.

Conclusions: The results of this meta-analysis suggest that the IL-4 -33C/T polymorphism is a risk factor for asthma.

Key words: Interleukin-4. Asthma. Polymorphism. Meta-analysis.