1. Mannino DM, Buist AS. Global burden of COPD: risk factors, prevalence, and future trends. Lancet. 2007;370(9589):765–73.
2. Johnson NB, Hayes LD, Brown K, Hoo EC, Ethier KA. CDC National Health Report: leading causes of morbidity and mortality and associated behavioral risk and protective factors— United States, 2005–2013. MMWR. 2014;63(Suppl-4):3–27.
3. Chronic Obstructive Pulmonary Disease (COPD). http://www.cdc.gov/copd/data.htm
4. Ford ES, Murphy LB, Khavjou O, Giles WH, Holt JB, Croft JB. Total and state-specific medical and absenteeism costs of COPD among adults aged >/= 18 years in the United States for 2010 and projections through 2020. Chest. 2015;147(1):31–45.
5. Wheaton AG, Cunningham TJ, Ford ES, Croft JB. Employment and activity limitations among adults with chronic obstructive pulmonary disease - United States, 2013. MMWR Morb Mortal Wkly Rep. 2015;64(11):289–95.