People who are obese and have asthma may carry a specific trait that causes them to have poorer control of their asthma than do individuals with asthma who are not obese.

Researchers examined 44 obese subjects with asthma and 44 nonobese subjects with asthma. Pulmonary function changes, methacholine-challenge scores, sputum-induction cell counts, symptom perceptions, BMI/waist circumference, and waist-to-hip ratios were compared between the two groups.

Study participants who were obese had poorer asthma control, as well as lower total lung capacity, expiratory reserve volume, functional residual capacity, and residual volume compared with those who were not obese.

Additionally, blood serum C-reactive protein and fibrinogen levels were higher in obese subjects than nonobese subjects. Bronchial and systemic inflammatory characteristics and patterns of pulmonary function changes suggest that obese patients may have a different phenotype of asthma.

This full study is published in the August issue of the journal CHEST.