Trends in prevalence of adult cough-related visits among all adult visits in US ambulatory care settings: 2003–2018 NAMCS and 2003–2018 NHAMCS data. Abbreviations: NAMCS: National Ambulatory Medical Care Survey; NHAMCS: National Hospital Ambulatory Medical Care Survey; ED: Emergency Department. a Ptrend were adjusted for age, sex, race, and payment source. b The weighted-estimate of the denominator (i.e., all adult visits) for each time period in NAMCS is 2.2 billion, 2.2 billion, 2.3 billion, 2.2 billion, 2.2 billion for 2003–2005, 2006–2008, 2009–2011, 2012–2014, and 2015–2018, respectively. The weighted-estimate of the denominator (i.e., all adult visits) for each time period in NHAMCS is 252.9 million, 277.0 million, 308.1 million, 312.7 million, and 421.5 million for 2003–2005, 2006–2008, 2009–2011, 2012–2014, and 2015–2018, respectively.