Effects of TNF-α polymorphisms on asthma risk: a systematic review and meta-analysis.

BACKGROUND Several studies have examined associations between TNF-α polymorphisms and asthma risk, but the results have been conflicting. METHODS A search was performed of the PubMed, EMBASE, and Wanfang databases. Data were extracted and pooled ORs with 95% CIs were calculated. RESULTS Fifty-four studies were included. A significant association between the TNFA-308A/G polymorphism and asthma susceptibility was observed for AA + AG vs GG (OR, 1.39; 95% CI, 1.23-1.58; P < .001). This polymorphism was also significantly associated with asthma risk in whites (OR, 1.47; 95% CI, 1.25-1.73; P < .001), atopic asthma risk (OR, 1.38; 95% CI, 1.16-1.65; P < .001), pediatric asthma risk (OR, 1.48; 95% CI, 1.23-1.79; P < .001), and adult asthma risk (OR, 1.35; 95% CI, 1.21-1.52; P < .001).There was also a significant association between the TNFA -857C/T polymorphism and asthma risk in the recessive model (OR, 1.25; 95% CI, 1.10-1.43; P < .001). In the subgroup analyses, asthma risk was significantly increased in Asians (OR, 1.23; 95% CI, 1.07-1.41; P = .004) and atopic individuals (OR, 1.33; 95% CI, 1.13-1.57; P < .001). No significant association was found for the TNFA-238A/G polymorphism. There were insufficient data to evaluate the associations between TNFA -1031T/C and -863C/A polymorphisms and asthma risk. CONCLUSIONS This meta-analysis suggests that TNFA -308A/G and -857C/T polymorphisms are risk factors for asthma.