An estimated 6.1 million children suffer from asthma, making the respiratory illness the most common chronic condition among kids, according to the American Lung Association. Now, new findings published in the journal Pediatrics suggest that overweight and obese youngsters face a higher risk of developing asthma compared with their healthy-sized counterparts, reports DukeHealth.

For the study, researchers at Duke University collaborated with the National Pediatric Learning Health System (PEDSnet) to review data for more than 500,000 children from more than 19 million doctor visits made between 2009 and 2015 at six major children’s health centers.

Kids considered to have asthma were diagnosed at two or more doctor’s appointments and given a prescription. Additionally, the disease was confirmed via lung function tests. Those classified as obese scored a body-mass index (BMI)—a ratio of height to weight—in the 95th percentile or above for their age and sex.

Scientists found a 30 percent and 17 percent increased risk for asthma in children who were obese and overweight, respectively, compared with kids of a healthy weight.

After using several models to calculate asthma risk and adjust for several factors, including socioeconomic status and allergies, researchers noticed similar results.

Researchers said this suggests that asthma could have been prevented in 1 million children between ages 2 and 17 if they maintained a healthy weight. “Obesity may be the only risk factor for childhood asthma that could be preventable,” said Jason Lang, MD, associate professor of pediatrics at Duke and the study’s lead author. “This is another piece of evidence that keeping kids active and at a health weight is important.”

Although further research is needed to determine whether being overweight or obese is a direct cause of asthma, Lang suggested that these findings reveal the significant role overweight plays in the development of childhood asthma.

Click here to learn why asthma inhalers don’t work equally well for all children.