Characteristics of the individual studies included in the systemic review and meta-analysis.

Ref references, Vs. versus, NS not significant, WA West Asian, EA East Asian, EU European, OR odds ratio, CI confidential interval, PFT pulmonary function test, ATS american thoracic society, NAEP national asthma education and prevention program, GINA global initiative for asthma, NIH national institute of health.†Odds ratio indicated asthma versus control group.‡Quality assessment scoring system according to Thakkinstian et al. [28], §Hardy-Weinberg equilibrium in deviation in control groups.*Haplotype of IL-10 -1082 G/A, -819 C/T and -592 C/A.