Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality. Global Burden of Disease studies have estimated that COPD is the third leading cause of death worldwide [1] and in the USA [2]. Mortality appears to be decreasing worldwide [3]; despite this, COPD still caused more than 3 million deaths in 2010 alone [1]. It is also the second leading cause of disability-adjusted life-years lost [4]. COPD-related mortality more than doubled among women over a 20-year observation period [5], and exacerbations now account for 50% to 75% of the costs associated with COPD [6].