COPD is the fourth leading cause of death worldwide, and the third leading cause of death in the United States. The death rate due to COPD increased over 100% between 1970 and 2002. No other major cause of death in the US has increased at this rate. Globally, COPD has been shown to be responsible for 3.8% of deaths in high-income countries and 4.9% of deaths in low-income countries. There is significant variability in the prevalence of COPD between countries. This may be due to differing rates of exposure to tobacco smoke and indoor and occupational pollutants. In the past, men have experienced higher rates of disease due to COPD. This difference has been thought to be due primarily to greater exposure to tobacco smoke and occupational pollutants. Surveys have shown that the prevalence of COPD appears to be becoming more equally distributed between men and women. COPD contributes a significant burden of healthcare costs. Exacerbations are responsible for much of the morbidity and mortality experienced by people with COPD, and the median number per year ranges between 1 and 3. It has been clearly shown that patients with more severe manifestations of COPD have greater rates of mortality over time. However, estimates of mortality may be underestimated, as deaths in this population are often attributed to other etiologies such as other respiratory disorders, lung cancer, and cardiovascular disease.
Acute exacerbations of COPD are commonly triggered by bacterial or viral pathogens, pollutants, or changes in temperature and humidity, and present with an acute-onset, sustained worsening of the patient's respiratory symptoms, lung function, functional status, and quality of life. Exacerbation rates and all-cause mortality tend to be higher during winter months. Acute exacerbations of COPD, particularly those that are moderate to severe, have significant public health impact, with increased healthcare utilization and healthcare costs and increased mortality. Early deaths among patients hospitalized with severe COPD exacerbation are often caused by concurrent problems such as pulmonary embolus, pneumonia, or CHF. Patients may also be at risk of myocardial infarction and stroke in the post-exacerbation period. 
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