Abstract

Background: Oxidative stresses including cigarette smoking are implicated in the pathogenesis of cerebrovascular diseases, which are associated with pneumonia because of frequent aspiration. Haem oxygenase-1 (HO-1) acts in cytoprotection against oxidants, provides anti-inflammatory effects, and inhibits atherogenesis. A (GT)_n dinucleotide repeat in the human HO-1 promoter modulates HO-1 gene expression and shows length polymorphism, which is grouped into three classes: class S (<27 repeats), class M (⩾27, <33 repeats), and class L (⩾33 repeats) alleles.

Objective: To investigate the correlation between the HO-1 gene polymorphism and development of pneumonia in elderly Japanese.

Methods: The length of the (GT)_n repeats was analysed in 200 elderly patients with pneumonia and 200 control subjects. The association of the HO-1 gene polymorphism with risk of pneumonia was estimated by logistic regression.

Results: The proportion of allele frequencies in class L, and the proportion of genotypic frequencies in the L-allele carriers (L/L, L/M, and L/S), was significantly higher in patients with pneumonia than in controls (20% v 10% in class L, and 34% v 18% in L-allele carriers). After adjustment for potentially confounding factors, both cerebrovascular disorders and HO-1 gene L-allele carriers were significant and independent risk factors for pneumonia. The adjusted odds ratio for L-allele carriers v non-L-allele carrier was 2.1 (95% confidence interval, 1.2 to 3.6).

Conclusions: The large size of a (GT)_n repeat in the HO-1 gene promoter may be associated with susceptibility to pneumonia in the older Japanese population.