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Body mass index and asthma severity in the National Asthma Survey.

Taylor B, Mannino D, Brown C, Crocker D, Twum-Baah N, Holguin F

Emory University, Atlanta, Georgia, USA.

BACKGROUND: The association between obesity and asthma severity remains controversial and limited to small studies. METHODS: 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. RESULTS: 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). CONCLUSIONS: In a large, diverse sample of adults with asthma, obesity was associated with measures of asthma severity after adjusting for potential confounders.

Published 24 December 2007 in Thorax, 63(1): 14-20.
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