Childhood asthma has made headlines in recent years because of an upward trend in the number of cases. That may have changed. A government study published in the journal Pediatrics, shows asthma rates may be leveling off or declining, but not for poor children. Researchers at the National Center for Health Statistics looked at asthma rates between 2001 and 2013 and found rates increased until 2009 when they plateaued. Then in 2013 rates began to decline except for children in poverty.

The researchers did not examine why the decline or leveling off is happening, but they say it may have to do with declines in air pollution and stabilizing childhood obesity rates.

Dr. Avni Joshi is a pediatric allergist and immunologist with the Mayo Clinic Children's Center. She says, "while the leveling off of childhood asthma is encouraging, it may be a bit too early to confirm there is actually a decline in rates. I think we need more data from 2013 to be absolutely sure. However, there does appear to be a leveling off of childhood asthma rates that mirror the rates of childhood obesity and exposure to secondhand smoke. This leveling of childhood asthma rates does not appear to be happening for children living in poverty where there is continued exposure to environmental risk factors such as smoke exposure, obesity and high levels of stress."

The Centers for Disease Control and Prevention says in the United States an estimated 6.8 million children have asthma, and for all ages the disease is responsible for 14.2 million trips to the emergency department.