Seasonality, ambient temperatures and hospitalizations for acute exacerbation of COPD: a population-based study in a metropolitan area

Almagro, Pere; Hernandez, Carme; Martinez-Cambor, Pable; Tresserras, Ricard; Escarrabill, Joan

Chronic obstructive pulmonary disease (COPD) is one of the most prevalent chronic diseases and is associated with high morbidity and mortality worldwide. Given that the prevalence of COPD increases with age, the perspective is that the impact of the disease will continue to increase in the near future. According to the World Health Organization, in 2005, COPD affected 210 million people, of whom 3 million died from the disease. 1 More recently, the Global Burden of Disease Study estimated that, in 2010, COPD was the third leading cause of death globally and ninth in disabilityadjusted life years. 2, 3 A great part of this mortality in COPD occurs during exacerbations and the subsequent weeks, especially in patients hospitalized for severe exacerbations. 4, 5 for exacerbation of their disease over a period of 3 years. 6 In addition, these hospitalizations generate the majority of health care costs and cause a significant deterioration in quality of life for affected patients. 6, 7 Factors associated with an increased risk of hospitalization include a prior history of admissions for COPD exacerbation, older age, severe pulmonary functional impairment, and the presence of comorbidities. 6, [8] [9] [10] [11] Recently, two publications based on data obtained in the TORCH and POET trials, (two large international studies involving over 13,000 patients) investigated the relationship between exacerbations and seasonality, and confirmed an increase in exacerbations during the winter months along with an increase in hospitalizations, although this association was not observed in the tropics. 12, 13 Both studies were performed by comparing seasons, and therefore only indirectly dealt with temperatures. There are few studies directly assessing the influence of temperature in exacerbations of COPD, especially in more severe cases, such as those requiring hospitalization.