The portion of people in the U.S. with asthma rose from 7.3 percent in 2001 to 8.4 percent in 2010, according to the report from the Centers for Disease Control and Prevention.
That means 25.7 million people had asthma in 2010, including 7 million who were younger than 18.
Over the same period, death rates from the condition dropped 33 percent. For every 10,000 people with asthma, there were 1.4 deaths in 2010, compared with 2.1 deaths in 2001.
The disorder has been linked with poverty, and the new findings showed that 11.2 percent of people living below the poverty level had asthma. However, asthma was also reported by 7.3 percent of those who earn at least twice the poverty level.
The findings also showed 9.2 percent of females had asthma in 2010, whereas the rate among males was 7 percent.
Asthma is a chronic airway disorder that can be triggered by exercise, infections, certain chemicals, airborne irritants such as tobacco smoke, or allergens such as pollen. During an asthma attack, the airway becomes obstructed because of inflammation and constriction of the surrounding muscles. It is not clear how to prevent asthma from developing, and there is no known cure, the CDC says.
The new findings are based on data gathered during the National Health Interview Survey, in which CDC researchers conducted household interviews with a nationally representative sample of participants.