U.S. asthma rates on the rise, CDC says

The number of Americans with asthma rose about 4 percent in 2002,and minority groups have a more difficult time controlling disease than whites, federal officials said Thursday. About 7.5 percent of Americans reported having asthma in 2002 -- the most recent year figures are available, the Centers for Disease Control and Prevention said. That is up from 7.2 percent a year earlier -- an increase of more than 4 percent.
About 16 million Americans have asthma, the CDC said.
Experts said they do not know why asthma rates are on the rise, although it is possible that the disease is diagnosed more often, said Jeanne Moorman, one of the study's authors.
Asthma has been on the rise since 1980. Between 1980 and 1996, cases nearly doubled from 3 percent to 5.5 percent of the population. CDC researchers do not compare those numbers with the most recent data because they have changed their survey questions since 1996.
Blacks, Hispanics, American Indians and Alaskan natives all had higher rates of asthma-control problems than whites and Asians. These groups were more likely to visit the hospital and report asthma attacks and disturbed sleep, the CDC said.
Asthma has no known cause, although some theories link it to diet and air pollution. Another is that children now are not exposed to enough germs in early life to mature their immune systems.