The impact on risk-factor analysis of different mortality outcomes in COPD patients

The aim of the present study was to analyse the role of potential selection processes and their impact when evaluating risk factors for 30-day mortality among patients hospitalised for chronic obstructive pulmonary disease (COPD). A cohort of 26,039 patients aged > or = 35 yrs and hospitalised with COPD were enrolled. A 30-day follow-up was carried out using both the cause mortality register (CMR) and the hospital discharge register (HDR). Individual and hospital factors associated with 30-day mortality were studied using both mortality outcomes. The 30-day mortality rate was 1.21.1,000 patient-days(-1) (95% confidence interval (CI) 1.14-1.29) using the CMR, and 1.06.1,000 patient-days(-1) (95% CI 0.98-1.13) using the HDR. Male patients, the most poorly educated, those who resided outside Rome and those who had more than one hospitalisation in the previous 2 yrs were more likely to die after discharge than when hospitalised. The most frequent cause of in-hospital death was respiratory disease and after discharge, heart disease. Older age, male sex, comorbidities, previous hospitalisations for respiratory failure, and admission to a ward not appropriate to treat respiratory diseases were the most important predictors of 30-day mortality. Using in-hospital 30-day mortality provides a significantly different estimate of the role of specific risk factors.