Body mass index and asthma in the military population of the northwestern United States.

BACKGROUND: Patients with asthma commonly have other medical problems such as obesity, but it is unclear if obesity independently relates to asthma occurrence.

OBJECTIVE: To examine the association between asthma and obesity.

METHODS: We studied enrollees aged 17 to 96 years in region 11 of TRICARE, a military managed health care program encompassing Washington, Oregon, and northern Idaho, using an enrollment questionnaire from January 1997 to December 1998. We performed case-control analyses on 2788 asthma cases and 39 637 controls. From these cases and controls, we selected a random sample of 1000 asthma cases and 1000 controls, linking them to a computerized military health record system to verify if medications indicated for asthma therapy were prescribed. After excluding cases not prescribed bronchodilator medications and excluding controls prescribed bronchodilator medications or steroids, we used logistic regression to estimate associations among asthma, body mass index, and demographic, lifestyle, and comorbid risk factors in 386 verified cases and 744 verified controls.

RESULTS: Increasing body mass index, younger age, female sex, non-active duty beneficiary status, and arthritis were significant independent predictors of asthma prevalence in both our larger analysis and our verified substudy, whereas stomach ulcer, depression, hypertension, and white race are also independent predictors of asthma prevalence in our larger analysis.

CONCLUSIONS: Increasing body mass index is a key factor predicting prevalence of asthma and, if determined to be etiologically related to asthma incidence, is a potentially modifiable risk factor for asthma.