Houston, Texas, USA : A study including health data for more than 500,000 children in the U.S. suggests obesity might be to blame for about a quarter (23 to 27 percent) of asthma in children who are obese.
This could mean about 10 percent of all kids ages 2 to 17 with asthma—almost 1 million children in the U.S.—might have avoided the illness by maintaining a healthy weight, according to researchers at Duke University and collaborators with the National Pediatric Learning Health System (PEDSnet). The findings will be published Nov. 26 by the journal Pediatrics.
“Asthma is the No. 1 chronic disease in children and some of the causes such as genetics and viral infections during childhood are things we can’t prevent,” said Jason E. Lang, M.D., associate professor of pediatrics at Duke and the study’s lead author. “Obesity may be the only risk factor for childhood asthma that could be preventable. This is another piece of evidence that keeping kids active and at a healthy weight is important.”
For the retrospective study, researchers analyzed data for 507,496 children from more than 19 million doctor’s visits at six major children’s health centers.
The data were entered into a clinical research data network called PEDSnet between 2009 and 2015.
Those classified as having asthma had been diagnosed at two or more doctor’s appointments and had also received a prescription, such as an inhaler. Tests of their lung function also confirmed they had the disease.
Children classified as obese—those with a body-mass index (BMI) in the 95th percentile or above for their age and sex—had a 30-percent increased risk of developing asthma than peers of a healthy weight. Asthma did not affect just those with obesity. Children who were overweight but not obese (BMI in the 85-94th percentile) also had a 17-percent increased asthma risk compared to healthy-weight peers.
The researchers calculated asthma risk using several models and adjusted for risk factors such as sex, age, socioeconomic status and allergies. The results remained similar.
The study has several limitations, Lang said, including that the data were collected during doctor’s visits and not in a controlled clinical research setting. Lang said more experiments are needed to prove overweight and obesity directly cause changes that lead to asthma because scientists don’t completely understand how or why this would occur.
Scientists have explored hypotheses including potential differences in how children’s lungs and airways develop when they are overweight, and inflammatory changes in the body due to obesity, Lang said.
Still, these findings and others, such as how asthma often improves with weight loss, suggests obesity plays a key role or is directly to blame, Lang said.
“I think it’s reasonable to be concerned that it’s a causal relationship,” Lang said. “It appears becoming overweight or obese as a child significantly increases your risk of developing asthma, and it’s a significant increase, directing attention again to the importance of preventing obesity at an early age.”
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.
A second study found that obesity may exacerbate asthma in children.
Citation : Jason Lang, M.D., M.P.H., associate professor of pediatrics, division of allergy, immunology and pulmonary medicine, Duke University School of Medicine, Durham, N.C.; Sophia Jan, M.D., chief of pediatrics, Cohen Children’s Medical Center, New Hyde Park, N.Y. Pediatrics.
Obesity may exacerbate asthma in children
In a Pediatric Allergy & Immunology study of children hospitalized for asthma, obesity was a risk factor for repeated hospital admissions.
The study included 38,679 patients, including 3177 underweight, 28,904 normal weight, 3334 overweight, and 3264 obese patients. Those in the obese group were more likely to be readmitted to the hospital within 30-days of discharge and to have longer hospital stays than those in the normal-weight group.
No significant difference was observed between the four groups regarding the need for intensive care and total hospitalization costs.
“Our investigations provide important information for the prevention of obesity in children with asthma,” wrote the authors of the study.
Explore further: Obese preschoolers have 60 percent higher healthcare costs than healthy weight children
Citation for second study: Yusuke Okubo et al, Impact of pediatric obesity on acute asthma exacerbation in Japan, Pediatric Allergy and Immunology. DOI: 10.1111/pai.12801
Video : Jason E. Lang, M.D., associate professor of pediatrics at Duke Health and the study’s lead author speaks about the research.
Image credit: Duke Health