Obesity Worsens Asthma

FRIDAY Sept. 5, 2008 -- New research shows that obese people who have asthma are nearly five times more likely to be hospitalized for the problem and to have lower quality of life and worse control of the disease than those with asthma who are normal weight.

Researchers from Kaiser Permanente, Massachusetts General Hospital and Harvard Medical School evaluated 1,113 adults with asthma, all members of Kaiser, in Oregon, Washington or Colorado.

They asked the patients about their weight, height, smoking habits, other illness, asthma treatment and their quality of life associated with asthma, as well as their asthma control and any hospitalizations related to the condition. They also computed their body-mass index (BMI).

"Even accounting for all of those factors, there was a pretty dramatic difference for obese asthmatics versus non-obese asthmatics," said study authors Dr. Michael Schatz, chief of the department of allergy at Kaiser Permanente, San Diego, and a clinical professor of medicine at the University of California, San Diego, School of Medicine.

"The most severe was a nearly five times greater risk for being hospitalized for asthma in the prior year," Schatz said. Obesity was defined as having a BMI of 30 or above.

The team reported its findings in the September issue of The Journal of Allergy and Clinical Immunology, found other differences associated with obesity. Obese patients with asthma were 2.8 times more likely to have day-to-day problems with quality of life associated with their disease. They were 2.7 times more likely to have poor asthma control, too.

In previous research, Schatz said, obesity has been associated with having more intense asthma.

For those who had asthma and were overweight but not obese, with a BMI of 25 to 29, the findings were not as clear, Schatz said. While the results for the overweight but not obese weren't significantly different than for those of normal weight, "we probably could have used more numbers," Schatz said, explaining that the numbers of overweight but not obese persons may have been too small to tease out a difference. "I wouldn't want to conclude that being overweight [with asthma] is the same as normal weight in terms of risks."

His advice for trying to keep asthma in check? "In general, the best bet would be to be at a normal weight," Schatz said.

The study adds to the base of knowledge about weight and asthma, said Dr. Christopher Cooper, a professor of medicine and physiology at the David Geffen School of Medicine, University of California, Los Angeles. "This adds additional evidence there is some association between the two," he said.

The study relied on large numbers overall, he said, and the statistics are sound. One limitation is the lack of an intervention, such as following obese asthmatics who lose weight to see if their condition improves, he added.

Exactly why obesity seems to make asthma worse is not known. In the study, Schatz and his colleagues speculated that obese people may have a lower self-image and not adhere to measures to make their asthma better, may not be as adherent to medication, or other factors.

More information

For more on asthma and what can trigger it, visit the U.S. Centers for Disease Control and Prevention.

Posted: September 2008


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