The-308 G/A polymorphism in TNF-α gene is associated with asthma risk: an update by meta-analysis

The -308 G/A polymorphism in TNF-alpha gene has been extensively investigated for association to asthma; however, results of different studies have been inconsistent. The aim of this study is to comprehensively evaluate the genetic risk of -308 G/A polymorphism in TNF-alpha gene for asthma. A meta-analysis was carried out to analyze the association between the -308 G/A polymorphism TNF-alpha gene and asthma risk. A total of 4717 cases and 5012 controls in 29 case-control studies were included in this meta-analysis. The result indicated that the variant A allele carriers had a 38% increased risk of asthma, when compared with the homozygote GG (odds ratio (OR) = 1.40, 95% confidence interval (CI), 1.13-1.68 for AA + AG vs. GG). In the subgroup analysis by ethnicity, significant elevated risks were associated with A allele carriers in Asians (OR = 1.53, 95% CI = 1.17-2.01 and P = 0.002) but not in Caucasians(OR = 1.06, 95% CI = 0.75-1.50 and P = 0.73). In the subgroup analysis by age, significant elevated risks were associated with A allele carriers in adults (OR = 1.44, 95% CI = 1.14-1.81, and P = 0.002) and children (OR = 1.37, 95% CI = 1.03-1.82, and P = 0.003). In the subgroup analysis by atopic status, significant elevated risks of asthma were associated with A allele carriers in atopic population (OR = 1.68, 95% CI = 1.34-2.10, and P < 0.00001) but not in non-atopic population (OR = 0.98, 95% CI = 0.58-1.68, and P = 0.95). Our results suggest that the TNF-alpha -308 G/A polymorphism contributes to susceptibility to asthma.