Increasing levels of body mass index - a measure of weight relative to height - are related to the risk of having asthma, according to Hutch and other Seattle-area researchers.
Dr. Anne McTiernan of the Public Health Sciences Division and colleagues conducted a study to examine the association between obesity and asthma, which affects about 6 percent of the general population.
Obesity is common in asthmatic individuals, but most studies on the relationship between the two conditions have focused on limited populations.
"This study is unique because of its size and relatively low cost, since we were able to use existing records of the military," said McTiernan, also a research associate professor of epidemiology and geriatrics at the University of Washington.
"It establishes a link between two common conditions in the U.S. - obesity and asthma. Twenty-five percent of the adult population is classified as obese, and 5 percent or more of the population has asthma."
The study was led by Dr. Sylvia Young, former graduate student in the UW Department of Epidemiology and now at the Navy Environmental and Preventive Medicine Unit in Sigonella, Italy. The study appeared in the July 9 edition of the Archives of Internal Medicine.
Dr. Jeffrey Gunzenhauser, of the Preventive Medicine Service at Madigan Army Medical Center in Tacoma, and Dr. Kathi Malone, Hutch PHS investigator, also took part in the project.
2,000 Northwest cases
Researchers selected a random sample of 1,000 asthma cases and 1,000 controls from a military-managed health-care program in Washington, Oregon, and northern Idaho. The enrollees, age 17 to 96, were linked to a computerized military health-record system to verify if medications indicated for asthma therapy were prescribed.
The scientists excluded those who were not prescribed bronchodilator medications and excluding controls who were prescribed bronchodilator medications or steroids, the authors estimated associations among asthma, body mass index (body weight in kilograms divided by the square of height in meters), and demographic, lifestyle, and other risk factors in 386 cases and 744 controls.
They found that increasing body mass index, younger age, female gender, non-active duty beneficiary status and arthritis were significant predictors of asthma prevalence. They also determined that stomach ulcer, depression, hypertension and Caucasian race were also predictors of asthma prevalence.
Patients with asthma commonly have other medical problems, such as obesity, but it is unclear if obesity independently relates to asthma occurrence. In the U.S. population, 54.9 percent of adults are overweight and 22 percent are obese.
Asthma cases 1 percent
In 1990, health-care expenditures for illness related to asthma were estimated at $6.2 billion, or nearly 1 percent of all U.S. health care costs.
Future research is required to determine whether obesity causes asthma and whether weight reduction in obese persons with asthma will reduce their symptoms, McTiernan said.