Chronic obstructive pulmonary disease (COPD) accounts for nearly three million deaths annually, with approximately 5% of deaths in Canada attributed to COPD in 2004. Mortality rates among individuals with COPD or asthma, however, are not extensively studied in North America. Certainly, follow-up of individuals with respiratory diseases can shed light on mortality risks and contribute valuable information to prevent premature death. Accordingly, this retrospective study investigated mortality rates and examined risk factors for premature death among patients diagnosed with respiratory diseases identified from two lung function testing databases of two respiratory clinics in Ontario during the 1990s.
Chronic obstructive pulmonary disease (COPD) and asthma are common; however, mortality rates among individuals with these diseases are not well studied in North America.
To investigate mortality rates and risk factors for premature death among subjects with COPD.
Subjects were identified from the lung function testing databases of two academic respiratory disease clinics in Hamilton and Toronto, Ontario. Mortality was ascertained by linkage to the Ontario mortality registry between 1992 and 2002, inclusive. Standardized mortality ratios were computed. Poisson regression of standardized mortality ratios and proportional hazards regression were performed to examine the multivariate effect of risk factors on the standardized mortality ratios and mortality hazards.
Compared with the Ontario population, all-cause mortality was approximately doubled among subjects with COPD, but was lower than expected among subjects with asthma. The risk of mortality in patients with COPD was related to cigarette smoking, to the presence of comorbid conditons of ischemic heart disease and diabetes, and to Global initiative for chronic Obstructive Lung Disease severity scores. Individuals living closer to traffic sources showed an elevated risk of death compared with those who lived further away from traffic sources.
Mortality rates among subjects diagnosed with COPD were substantially elevated. There were several deaths attributed to asthma among subjects in the present study; however, overall, patients with asthma demonstrated lower mortality rates than the general population. Subjects with COPD need to be managed with attention devoted to both their respiratory disorders and related comorbidities.