WEDNESDAY, March 16, 2016 (HealthDay News) -- As weight rises, so too does the risk for asthma, U.S. health officials report.
During the 2011-2014 period, nearly 9 percent of American adults had asthma. Normal-weight folks had asthma rates around 7 percent, while about 8 percent of overweight people had the illness.
For obese American adults, asthma rates topped 11 percent, the new research said.
Obese women had the highest rates -- almost 15 percent had the respiratory ailment, researchers found.
"Why obese people are more likely to have asthma is unknown," said lead researcher Dr. Lara Akinbami, a medical officer at the U.S. Centers for Disease Control and Prevention's National Center for Health Statistics. "We just know they have a higher risk."
It is clear that "obesity is the risk for asthma, not the other way around," she said.
But, the study wasn't designed to prove a cause-and-effect relationship between obesity and asthma. It only showed an association between these factors.
It's unknown if losing weight reduces asthma, Akinbami said. But preventing obesity and controlling asthma are both possible, she said.
"This study really confirms that obesity is a risk factor for asthma -- they are very tightly linked," Akinbami said.
Asthma is a chronic disease of the airways. Symptoms include shortness of breath, wheezing, chest tightness and cough, according to the U.S. National Heart, Lung, and Blood Institute.
Akinbami and her colleague Cheryl Fryar, a health statistician, used data from the 2001-2014 U.S. National Health and Nutrition Examination Survey for the new report.
Among women, 15 percent of obese women suffered from asthma, compared with 8 percent of normal-weight women and 9 percent of overweight women, the research showed. The asthma rate did not differ significantly by weight for men, the researchers said.
Why obese women have a higher risk of asthma than men isn't clear. However, Dr. Len Horovitz, a pulmonologist at Lenox Hill Hospital in New York City, speculated that hormones might account for the difference. "That's something we do not know at this point," he said.
The rates of asthma were higher among all obese adults regardless of race or age, compared with normal-weight adults, the researchers noted.
The prevalence of asthma among all adults increased in 2001-2002 from 7.1 percent to 9.2 percent in 2013-2014. This increase was driven by greater asthma rates among overweight adults, not by increases among obese or normal-weight adults, the researchers said.
Horovitz said the connection between obesity and asthma might be because excess weight makes it harder to breathe, and losing weight makes breathing easier.
"There are many reasons not to get obese," Horovitz said. "The fear of asthma is not at the top of the list. High blood pressure and diabetes are above that, but sure, asthma is another reason," he said.
Findings from the new research were published March 16 in a report from the U.S. National Center for Health Statistics.
For more information on asthma, visit the U.S. National Heart, Lung and Blood Institute.