U.S. asthma rates rising but reasons unclear: CDC

About 25 million Americans, or 1 in 12 people, have asthma, a figure that is rising despite efforts to control key asthma triggers such as indoor smoking, U.S. government researchers said on Tuesday.

According to the U.S. Centers for Disease Control and Prevention, an additional 4.3 million people were diagnosed with asthma from 2001 to 2009. The life-long disease causes wheezing, tightness in the chest, coughing and shortness of breath.

Asthma diagnoses increased among all demographic groups between 2001 and 2009, but children were hit hardest, with asthma affecting 9.6 percent of children, compared with 7.7 percent of U.S. adults.

The biggest increase in asthma rates was among black children, rising almost 50 percent from 2001 through 2009. Seventeen percent of non-Hispanic black children had asthma in 2009, the highest rate among racial/ethnic groups.

The cost of treating asthma rose about 6 percent to $56 billion in 2007, from $53 billion in 2002, according to the most recent figures. For patients, that's about $3,300 a year.