Body mass index and asthma severity in the National Asthma Survey

The association between obesity and asthma severity remains controversial and limited to small studies.

We determined the association of body mass index (BMI) and asthma severity in the National Asthma Survey. We included adults (age > or = 18 years) who self-reported symptoms of asthma in the past 5 years. A total of 3095 patients were divided into the following BMI categories: 1080 (35%) non-overweight (BMI < 25), 993 (32%) overweight (BMI > or = 25 and < 30) and 1022 (33%) obese (BMI > or = 30). Asthma severity measures included respiratory symptoms, healthcare utilisation, medication use, missed work days and the Global Initiative for Asthma (GINA) severity classification. Models were adjusted for: gender, race, age, education, income, employment status, smoking status, family history of asthma, state of residence and residence in a metropolitan statistical area.

Compared with non-overweight subjects, obese subjects with asthma were more likely to report continuous symptoms (OR 1.66, 95% CI 1.09 to 2.54), miss more work days (OR 1.35, 95% CI 1.01 to 1.81), use short acting beta agonists (OR 1.36, 95% CI 1.06 to 1.75), use inhaled corticosteroids (OR 1.34, 95% CI 1.01 to 1.79) and use any controller medication according to GINA guidelines (OR 1.37, 95% CI 1.01 to 1.85). Also, obese respondents were less likely to be in asthma remission (OR 0.56, 95% CI 0.38 to 0.82) and were more likely to have severe persistent asthma (GINA IV) (OR 1.42, 95% CI 1.05 to 1.90).

In a large, diverse sample of adults with asthma, obesity was associated with measures of asthma severity after adjusting for potential confounders.