Chronic Chlamydia pneumoniae infection is a risk factor for the development of COPD

Acute and convalescent sera were analysed for specific IgG and IgA Cpn antibodies using microimmunofluorescence. Chronic Cpn infection, defined as persistent elevated titres of IgA⩾1/64, was present in 85 patients. Chronic infection was associated with smoking and higher age, but no gender difference was observed. Thirty patients had COPD, defined as FEV1/FVC <70% without any features of asthma. Patients with COPD were older than those without, and there was no association with gender in this group. A statistically significant association, remaining after correction for smoking, was observed between chronic Cpn infection and COPD, and there was a trend for decreasing lung function with increasing antibody titres. The results suggest that chronic Cpn infection may be an independent risk factor for the development of COPD.