MONDAY, Nov. 26, 2018 (HealthDay News) -- The wheezy lung disease asthma is yet one more problem linked to excess weight in childhood, a new study suggests.
The research contends that as many as 10 percent of pediatric asthma cases in the United States could be avoided if childhood obesity were eliminated.
"There are very few preventable risk factors for asthma -- obesity may actually be the only one. About 6 to 8 million kids have asthma, so if 10 percent of these cases were removed (by eradicating obesity) that would be up to 800,000 kids without asthma," said the study's lead author, Dr. Jason Lang.
He's an associate professor with Duke University School of Medicine's division of allergy, immunology and pulmonary medicine, in Durham, N.C.
About 18 percent of children in the United States are obese. This can impair their quality of life and boost the risk of chronic illnesses, the study authors said.
Although adult asthma and obesity have been linked, there's been debate about whether obesity is a factor in childhood asthma, the researchers explained. The current study sought to address some of the concerns with previous research, Lang said.
The new research looked at data from more than a half-million children and about 19 million doctors' visits. These visits took place at one of six major children's health centers across the United States.
The children were diagnosed with asthma at two or more doctor's appointments. They were also given lung function tests (a step missing in some previous research), and a prescription, such as an inhaler, to treat their asthma.
Children who were obese were 30 percent more likely to be diagnosed with asthma. Kids who were overweight had a 17 percent increased risk of asthma, the findings showed.
How could excess weight lead to asthma?
No one knows for sure yet. And this study doesn't prove a cause-and-effect relationship.
But there are several theories, Lang said. One is that children who are obese may have alterations in lung growth that might lead to smaller airways, which would allow for more airflow obstruction. It's possible that obesity can lead to changes that make the lungs more over-reactive, he suggested.
Lang said it's also possible that other conditions linked to obesity -- such as acid reflux or sleep apnea -- might contribute to asthma. "Or, it may not be that it's just one thing. It may be a combination," he said.
Dr. Sophia Jan, chief of pediatrics at Cohen Children's Medical Center in New Hyde Park, N.Y., said the link between the two conditions isn't clear, but inflammation caused by obesity may play a role. She also suggested that certain genes may underlie both conditions.
And, finally, "Once a child has developed obesity, the weight in their chest and upper body probably exerts weight on their lungs, thereby affecting the lung's overall ability to expand and function," she said. Jan also suspects that multiple factors link obesity and asthma.
So, what can parents do?
According to Lang, "There is literature that shows when kids and adults do lose weight, their asthma gets much better and may even go away completely."
He noted that physical activity is an important part of any weight loss efforts and suggested kids follow recommended guidelines and get at least an hour a day of activity.
"Activity expands the lungs and gives periods of high ventilation. It's healthy for lungs to do that," Lang said.
Jan added that maintaining a healthy weight is healthy for many reasons.
"Besides the long-term cardiovascular benefits -- preventing heart disease, stroke and diabetes -- there are numerous short-term benefits, including decreasing the risk of sleep apnea, heartburn, gallstones, muscle and joint pain, poor self-esteem, anxiety and bullying," she said.
And, now, preventing or minimizing the severity of asthma can be added to that list, she noted.
Results of the study were published online Nov. 26 in Pediatrics.
To learn more about the connection between weight and asthma, go to the American Lung Association.