Epidemiological studies of severe infections in COPD

Sammanfattning: It is well known that patients with COPD have an increased risk of lower respiratory tract infections, but less is known about the association with other infections. The aim of this thesis was to explore epidemiological aspects of severe infections in COPD, using public registries in Sweden. In the first study, incidence rates of tuberculosis were compared in all individuals discharged with COPD, 1987-2003, with reference individuals from the general population. COPD patients were found to have a three-fold increased incidence of active tuberculosis. In the second study, incidence rates of tuberculosis were examined in participants in a health screening programme 1974-1992 who performed a spirometry at baseline. The risk of tuberculosis was found to be inversely correlated with the level of lung function. In the third study, a discharge diagnosis of COPD was validated against the original medical files. The degree of certainty of the COPD-diagnosis varied and around 10% were considered to be misclassified. In the fourth study, we compared the incidence rates of bacteraemia in individuals discharged with a COPD diagnosis, 1990-2003, and controls. COPD patients had a 2.5-fold increased incidence of bacteraemia which was paralleled by an increased risk of hospitalisation for infectious diseases. In the fifth study, the association between invasive pneumococcal disease and an underlying pulmonary disease was assessed, comparing pneumococcal cases from Southern Sweden, 1990-2008, to controls. Several chronic pulmonary diseases increased the risk of invasive pneumococcal disease but did not influence the mortality risk. Our findings show that COPD confers susceptibility to a broad spectrum of severe infections. Increased awareness could benefit these patients, reducing morbidity and mortality.