New research breaks down the link between obesity and asthma.

Share on Pinterest
Researchers wanted to know why obesity increased the risk of asthma. Photo: Getty Images

Obesity is the root cause of some of our most serious health issues: diabetes, hypertension, and cardiovascular disease, to name a few.

Researchers also know that obesity is linked to an increased risk for asthma. People with a high body mass index — roughly 30 percent or more — usually have ongoing, low-grade inflammation throughout the body. This includes their airways.

But a new study published this month in the American Journal of Physiology-Lung Cellular and Molecular Physiology looked at a potentially different link between obesity and asthma. The study showed that during an asthmatic episode, the smooth muscle cells from obese patients contract more than smooth muscle cells in nonobese patients.

Even though the study is the first of its kind, experts that Healthline talked to say these findings could give rise to a new method of diagnosis and treatment for obese and asthmatic patients.

“I think the study is an early step toward understanding the molecular mechanisms that cause the differences in asthma prevalence and severity,” Dr. Emily Pennington, a pulmonologist at the Cleveland Clinic, told Healthline.

One of the biggest findings from the study is that it overturns the notion that low-grade inflammation is the root cause of asthma among obese patients, according to Dr. Stokes Peebles, a pulmonologist and allergy specialist at Vanderbilt University Medical School.

”It’s not just the inflammation, it’s the smooth muscles,” he told Healthline. “The smooth muscles are different between someone who has obesity and someone who doesn’t.”

That’s key, because smooth muscle cells control the diameter of our airways, according to Dr. Reynold Panettieri. Panettieri is the vice chancellor for Translational Medicine and Science, as well as director at the Rutgers Institute for Translational Medicine and Science. He is also one of the study’s authors.

During optimum conditions, the smooth muscles in our airways are relaxed. We breathe in and out with little consternation. But add an irritant to the mix, such as an allergen, and the conditions in your airway will change.

“It’s the intrinsic nature in these cells,” he told Healthline. “If that muscle contracts more, then there is more obstruction, tightening of the chest.”

The research may also help to explain another conundrum that physicians face when treating obese patients who have asthma. Many don’t find relief when using traditional steroid inhalers, unlike nonobese patients.

“The treatment is the same, but obese patients don’t respond well,” Peebles said.

For the study, researchers took samples cells from cadavers with diagnosed obesity, and cadavers that did not have obesity. Both groups also had diagnosed asthma. The cells were divided up between genders.

Both sets of cells were subjected to histamines, a chemical that the body makes in response to an allergen exposure, and carbachol, a drug that can simulate what happens when muscles contract.

The smooth muscle cells culled from the obese subjects showed more “shortening” or contraction than the cells derived from the nonobese subjects. The cells derived from females also contracted more than cells derived from males.

This gender disparity also mirrors current asthma rates among men and women. Studies show that women who are obese tend to have higher rates of asthma compared to men who are obese. According to the report, the Centers for Disease Control and Prevention (CDC) shows that among obese adults, women were more affected than men, roughly 15 percent versus 7 percent.

In general, as the obesity rate continues to rise in the United States, so does the asthma rate. According to 2010 statistics from the CDC, roughly 40 percent of adults who are obese also have asthma. For nonobese adults, the asthma rate is around 27 percent.

Peebles said the study presents a new set of questions around the best way to treat asthma in obese patients, and whether new therapies should be considered.

Treatment for this specific group of asthmatics may need to shift to targeting the muscle, according to Panettieri.

“Relaxing the muscle,” he said, “targeting the muscle cells with long-acting dilators.”

Pennington said she hopes that further studies will help identify the exact mechanisms in these cells that are causing asthma disparity between obese and nonobese patients.

Research that “looks directly at the hyperresponsiveness of these cells,” she said.

A new study published this month in the American Journal of Physiology-Lung Cellular and Molecular Physiology found that during an asthmatic episode, the smooth muscle cells from obese patients contract more than smooth muscle cells in nonobese patients.

Experts say this means obesity may narrow the airway leading to asthma. It also means that common treatment for asthma: steroids, will be less effective for these patients, and other methods should be considered.