TUESDAY, March 2 (HealthDay News) -- Asthma rates are increasing across the United States, a new government study shows, but certain states have significantly lower rates of the respiratory disease.
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The overall rate of asthma is currently estimated to be 7.85% of the population, an increase of about 0.5% every three years. But, the report also found that some states have dramatically lower rates of asthma. For example, the study found that while almost 11% of people in Rhode Island had asthma, just 5% of those living in Louisiana had the illness.
"Asthma is a very common condition," said study author Dr. Teresa Ann Morrison, a medical officer in the Air Pollution and Respiratory Health Branch of the National Center for Environmental Health, in Atlanta.
"Our findings indicated wide differences in geographic prevalence among adults across the state level and an overall increased prevalence," she added.
Results of the study were to be presented Tuesday at the American Academy of Allergy, Asthma & Immunology annual meeting, in New Orleans.
For the study, Morrison and her colleagues culled data on adults with asthma from the Behavioral Risk Factor Surveillance System from 2000 to 2008. They broke the data into three-year increments (2000-2002, 2003-2005 and 2006 to 2008) so they could average the incidence of asthma over three years.
National three-year averages rose consistently by 0.5%. Overall, the incidence of asthma in adults was 7.85%, the study found.
Only one state -- Nevada -- experienced a decline in asthma incidence, but the difference wasn't statistically significant.
The prevalence of asthma varied significantly from state to state, with Louisiana reporting the lowest incidence at 5.04% and Rhode Island posting the highest incidence at 10.68%.
Nineteen states had larger-than-average increases, and the states with the two highest increases were Oklahoma with a 2.03% increase and Alabama with a 1.91% increase.
Morrison said there are a lot of theories as to why these geographic differences exist, but her study wasn't designed to tease out the reasons, only to identify the disparity.
"Asthma is very multi-factorial, and these differences can be due to a lot of different things. These findings are a call to engage further studies because these differences may help us understand the causes of asthma, help manage the disease and design state-specific interventions," she explained.
Dr. Jennifer Appleyard, chief of allergy and immunology at St. John Hospital and Medical Center in Detroit, said: "The fact that rates are consistently going up jibes with my clinical impression that prevalence is increasing. But, it's hard to tell what's causing the differences among the states. Because asthma is so complicated, I don't know if it's just one thing. It's probably a whole host of reasons, such as geography and who seeks health care."
If you already have asthma, Morrison said, it's important to make sure you have a "medical provider that understands asthma, [and] works with you to develop an asthma action plan to help you control your asthma exacerbations. You need to be followed up routinely, so make sure you have a good medical home."
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SOURCES: Teresa Ann Morrison, M.D., M.P.H., medical officer, Air Pollution and Respiratory Health Branch, National Center for Environmental Health, U.S. Centers for Disease Control and Prevention, Atlanta; Jennifer Appleyard, M.D., chief, allergy and immunology, St. John Hospital and Medical Center, Detroit; March 2, 2010, presentation, American Academy of Allergy, Asthma & Immunology annual meeting, New Orleans