ABSTRACT
I. Epidemiology of COPD Exacerbations There has been considerable interest in the causes and mechanisms of exacerbations of chronic obstructive pulmonary disease (COPD) as exacerbations are an important cause of the considerable morbidity and mortality associated with COPD (1). COPD exacerbations increase in frequency and severity with increasing severity of the underlying disease. Some patients are prone to frequent exacerbations that are an important cause of hospital admission and readmission, and these “frequent exacerbations” experience a particular burden on quality of life, disease progression, and mortality (2) (Fig. 1). COPD exacerbations are also associated with physiological deterioration and increased airway inflammation (3). These events are caused by a variety of factors such as viruses, bacteria, and probably common pollutants. COPD exacerbations are commoner in the winter months and there may be important interactions between cold temperature and exacerbations caused by viruses or pollutants (4).
