Abstract
BackgroundPrevious studies evaluated the association of IL-4 C33T polymorphism and risk of bronchial asthma but failed to establish a consistent conclusive association. In the present meta-analysis, we intend to define a more reliable estimate of the association in the presence of filling published literature.MethodsAn exhaustive search in Web of Science, Scopus, and PubMed databases was performed to identify all relevant publications before September 2020, and 24 publications (28 studies) with 6587 cases and 8408 controls were included in final analysis. The association between polymorphism and risk of asthma were measured by Odd ratios (ORs) and 95% confidence intervals (CIs). Moreover, Cochran’s Q and the I2 statistics were used to evaluate the degree of heterogeneity between studies.ResultsIn the overall study populations, a significant positive association was detected under all genotype models and announced the IL-4 C33T polymorphism as a potential risk factor in the pathogenesis of asthma. In the subgroup analysis by age, a significant association between IL-4 C33T polymorphism and risk of asthma in different age groups was identified in allelic model, which highlighted the predisposing role of the T allele for the asthma risk in all three age groups. Furthermore, the results of subgroup analysis by continent were heterogenous. Accordingly, IL-4 C33T polymorphism was a risk factor in Europeans (all models except heterozygote comparison), Americans (all models except recessive and homozygote comparison) and Asians (just recessive and allelic model). Finally, the ethnicity-specific analysis disclosed a significant association between IL-4 C33T polymorphism and asthma risk in Caucasians (all genotype models except heterozygote comparison), while this association was not significant in African-Americans.ConclusionsThis study suggests that IL-4 C33T polymorphism potentially acts as a risk factor for asthma in different ethnicities and age groups.
Highlights
Previous studies evaluated the association of interleukin 4 (IL-4) C33T polymorphism and risk of bronchial asthma but failed to establish a consistent conclusive association
Search strategy A comprehensive systematic search was applied through three major databases (MEDLINE, web of science, and Scopus) to find all potential publications considering the association between IL-4 C33T polymorphism and asthma risk released before September 2020
The results rejected significant association between IL-4 C33T polymorphism and risk of asthma in different age group except for allelic model [adults (OR = 1.14, 95% confidence intervals (CIs) = 1.02–1.26, P = 0.02, fixed effect model (FEM)), mixed (OR = 1.14, 95% CI = 1.01–1.29, P = 0.03, random effect model (REM)), children (OR = 1.13, 95% CI = 1.04–1.24, P = ≤0.001, FEM)] and recessive model (just in children (OR = 1.18, 95% CI = 1.03–1.35, P = 0.01, REM)) Fig. 3
Summary
Previous studies evaluated the association of IL-4 C33T polymorphism and risk of bronchial asthma but failed to establish a consistent conclusive association. There are several studies in which association between IL-4 C33T polymorphism and asthma risk have been evaluated [5, 6, 10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31] This association remains inconsistent and inconclusive in several studies. We conducted a meta-analysis to conclude a more exact estimation of the relation between the IL-4 C33T polymorphism and risk of asthma
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