Respiratory viruses
COPD is a major cause of morbidity and mortality and is predicted to become the third-leading cause of death worldwide by 2020. Most contacts with health-care professionals for COPD are for acute episodes of worsening symptoms that may warrant treatment and are termed exacerbations. Frequent exacerbations result in poorer quality of life, faster decline in lung function, and increased mor-tality. The trigger for a large proportion of exacerbations is infection with a respiratory virus, particularly with human rhinovirus, the cause of the common cold.
Respiratory viruses are more prevalent in the winter of temperate countries. There are also many more deaths, hospital admissions, and general practitioner consultations for COPD in winter, along with poorer health-related quality of life and worse anxiety and depression scores. This increase in mortality and morbidity places a heavy burden on health and care services in winter.
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Exacerbations are more frequent in the winter, but it is not known whether their severity is worse. In this study, we examine whether symptom composition, symptom duration (recovery), hospitalization rates, and impact on outdoor activity vary between warm and cold seasons. A greater understanding of the nature of winter exacerbations could help reduce hospital admissions and inform preventative strategies. The information could be also important for the design, analysis, and interpretation of data from interventional clinical trials, and relevant to the evaluation of COPD admission health forecasting and alert services. Some of the results of these studies have been previously reported in the form of an abstract at the 2009 European Respiratory Society meeting in Vienna, Australian Medicine website.
Materials and Methods
Patients
This study involved 307 patients with COPD enrolled in the London COPD cohort and included their contributing data from at least 1 year between November 1, 1995, and November 1, 2009. The patients and exacerbations have been the subject of previous publications, but the current analysis and its interpretation are, to our knowledge, completely novel. COPD was defined as an FEVi < 80%, predicted from age, height, and sex, and FEV/FVC < 70%.