Across the country, hospital emergency rooms are seeing a record number of patients — 145.6 million a year, according to the National Center for Health Statistics, part of the Centers for Disease Control and Prevention. The data — gathered in 2016 and released this month — show that most people head to an ER because of an illness rather than an injury. Stomach or abdominal pain tops the list of reasons (affecting 12.5 million patients), followed by chest pain (7.6 million) and fever (5.5 million). Among injuries treated in ERs, the most common result from a fall (10.5 million) or a motor vehicle crash (3.7 million). Although the number of ER patients is growing — in 2016, up 8.7 million from the year before — fewer people seem to be turning to ERs for routine care. The number of people seeking treatment for what ER doctors determine to be non-urgent symptoms has actually dropped, from 5.5 percent to 4.3 percent of all ER patients. But, as the American College of Emergency Physicians noted in its review of the data, “nearly two-thirds of [ER] visits occur after business hours, when other doctors’ offices are closed.” The picture painted by CDC data also shows that, once people get to an ER, 39 percent are being seen in 15 minutes or less, and 72 percent in less than an hour. Although people of all ages seek care at ERs, about 19 percent of patients in 2016 (27.4 million) were 15 or younger and 16 percent (23.1 million) were 65 or older. The CDC data, culled from the agency’s 2016 National Hospital Ambulatory Medical Care Survey, included information from only ERs that are part of a hospital and did not include information from free-standing emergency departments or urgent-care centers.