In the first study to adjust for risk factors that might explain the link between obesity and asthma, researchers found that obese individuals with asthma are nearly five times more likely to be hospitalized than non-bese asthma patients.

Of the 20 million Americans diagnosed with asthma, one third of them are obese (defined by the Centers for Disease Control as having a body-mass index of 30 or greater). The study found that obese people with asthma have significantly worse asthma control and a lower asthma-related quality of life compared to those who are not obese. Additionally, this population was found to be younger and use more oral corticosteroids than nonobese people with asthma.

To conduct the study, researchers interviewed 1,113 patients in Oregon, Washington, and Colorado who have persistent asthma and are age 35 or older. Patients were interviewed about qualities such as smoking habits, asthma-related quality of life, asthma control, weight, and height.

“The big finding here is that even after adjusting for risk factors, obese adults were nearly five times more likely to be hospitalized for their asthma. Given that 30% of our country in obese, this study is yet another example of the long-term dangersof obesity, along with heart disease, diabetes, stroke, and dementia,” says lead author David M. Mosen PhD, MPH.

The Kaiser Permanente study is published in the September issue of the Journal of Allergy and Clinical Immunology.