The feasibility of COPD surveillance in Ontario: a population study.

The Issue Chronic obstructive pulmonary disease (COPD), also known as emphysema or chronic bronchitis, is a progressive chronic respiratory disorder characterized by non-reversible obstruction of the airways in the lungs. It is characterized clinically by shortness of breath, cough, sputum production, wheeze and limited exercise tolerance and can lead to respiratory failure and death. While prevalence estimates vary widely depending on geographical and socio-demographic patterns, the prevalence of COPD remains high in adults over the age of 40 years, ranging from 2 to 22% depending on the definition used and the method for ascertaining positive COPD status (Gershon et al. 2010; Halbert et al. 2006). Despite the high prevalence in the general population, several authors note that COPD remains under-diagnosed globally (Hill et al. 2010; Huchon et al. 2002; Schirnhofer et al. 2007; Zielinski et al. 2006). This under-diagnosis has often been attributed to a lack of symptom recognition in patients who do not have obvious risk factors (Buist et al. 2007); however, others have confirmed that the problem exists in those with obvious risk factors, such as a history of smoking (Hill et al. 2010). Mild to severe forms of COPD are associated with considerable mortality, morbidity and decreased quality of life (Garrido et al. 2006). COPD is currently the fourth leading cause of death both in Canada and globally (Buist et al. 2007; O’Donnell et al. 2007), and among chronic diseases it is the only leading cause of death that is increasing (Lopez et al. 2006). It is projected that COPD will be the fifth leading cause of disability-adjusted life years (DALYs) globally by 2020 (Murray and Lopez 1997). Despite its substantial impact, COPD does not receive the same recognition as other diseases of comparable burden (Barnes and Kleinert 2004). It has been suggested that in developed nations such a lack of public awareness of the disease and its co-morbidities is in part due to the view that COPD is a consequence of people’s own actions (i.e., smoking) (Barnes and Kleinert 2004). For example, a recent analysis by the UK Clinical Research Collaboration (2006) found that respiratory diseases (including COPD) rated fourth highest in terms of DALYs but only 13th highest in terms of research spending – the largest discrepancy between disease burden and spending of all the disease areas studied. Similar findings have been demonstrated for COPD funding in the United States (Gillum et al. 2011). Given the immense burden that COPD places on the individual and society in terms of mortality, morbidity and direct and indirect costs, several organizations (Centers for Disease Control and Prevention 2011; European Respiratory Society 2011; Public Health Agency of Canada 2011) have called for COPD surveillance systems to aid in the development and targeting of public health programs and policies. There are several challenges to developing such a comprehensive population-based surveillance system (Chapman et al. 2006). First, one of the most important barriers has been the lack of a clear definition of COPD (Chapman et al. 2006; Mannino 2002). Second, population-based surveillance systems by nature are costly both in time and resources. And, third, it has been suggested that public support of healthcare funding for the surveillance of a disease perceived to affect mostly the elderly (Chapman et al. 2006) and smokers (Voelkel 2000) might be weak. A solution to some of these challenges might be the use of health administrative data as a surveillance tool. In Ontario, we have access to universal healthcare administrative databases containing information on hospitalizations, ambulatory visits and emergency visits linked together at the individual level. Given the capacity to follow a large and complete population, this study was undertaken to (1) determine the feasibility of using health administrative databases for the surveillance of COPD; and (2) provide an indication of the prevalence, incidence and mortality associated with COPD in the Ontario population. Furthermore, regional-level analysis was completed to demonstrate how variation in COPD rates might be used to identify areas with high current and future burden and to assist in policy and program implementation.