Genetic polymorphism of heme oxygenase 1 promoter in the occurrence and severity of chronic obstructive pulmonary disease: a meta‐analysis

Heme oxygenase 1 ( HMOX 1) plays an important role in the development of chronic obstructive pulmonary disease ( COPD ). However, the association of HMOX 1 length polymorphism in promoter region to the risk and severity of COPD has not been well studied. In this study, we searched the databases including PubMed, EMBASE , Cochrane Library and China National Knowledge Infrastructure ( CNKI ) and extracted the information from related articles. Pooled odds ratios ( OR s) and 95% confidence intervals ( CI s) were calculated to study the effect of HMOX 1 polymorphism on the risk and severity of COPD . As a result, nine studies were included for this meta‐analysis. Higher frequencies of L allele and type I genotype (containing at least one L allele) were found in patients with COPD (for L allele, OR 2.02, 95% CI : 1.32–3.11, P = 0.001; for type I genotype, OR 1.82, 95% CI : 1.28–2.61, P = 0.001), especially in Asian population (for L allele, OR 2.23, 95% CI : 1.68–2.95, P < 0.001; for type I genotype, OR 2.02, 95% CI : 1.51–2.70, P < 0.001). Genotyping method, source of control subjects, literature quality and language also affected the results to some extent. However, there was little difference in HMOX 1 genotypes distribution in patients with COPD with different severity. Our study indicated L allele and type I genotype were related to the susceptibility but not the severity of COPD .