More than three million U.S. adults may have inflammatory bowel disease, according to a new government estimate. That’s nearly triple the number of some previous estimates, the researchers said. The new estimate is based on a national survey conducted by researchers at the Centers for Disease Control and Prevention (CDC). Survey respondents were asked whether a doctor or other health professional had ever told them that they had either Crohn’s disease or ulcerative colitis, which are the two types of inflammatory bowel disease (IBD). Based on the responses, the researchers estimated that 1.3 percent of U.S. adults, or 3.1 million Americans, have IBD.

People with IBD have chronic inflammation in the gastrointestinal tract. Patients often have abdominal pain, cramping, fatigue and diarrhea. They may also have a poor quality of life, as they often have complications and need to be hospitalized or undergo surgery, the report said. The report additionally found that IBD is more common in some groups, including adults ages 45 and older, Hispanics, non-Hispanic whites, and adults with less than a high school level of education. The report found that 1.5 percent of adults ages 45 to 64, and 1.7 percent of adults ages 65 and older said they had been diagnosed with IBD. In the new report, the researchers looked at data gathered in 2015 during the CDC’s annual National Health Interview Survey. In this survey, researchers conduct in-person interviews with participants from across the U.S. about a broad range of health topics. Previous estimates of IBD prevalence in the U.S. have come from surveys done in limited geographic areas, or from health care claims data. For example, a study published in 2013 used claims data from 12 million people and estimated that 1.2 million U.S. adults had IBD. A 2007 study, based on the residents of one county in Minnesota, estimated that, nationally, 1.1 million people had the disease. The new report was published Oct. 28 in the CDC’s Morbidity and Mortality Weekly Report.