Abstract
Introduction: Obesity is a risk factor for asthma-like symptoms. Small airway involvement has been linked to difficulties in controlling asthma. Forced Vital Capacity (FVC) fall at PC20 has been suggested as a potent marker of distal airway abnormalities. Whether obesity is associated with increased distal airway involvement remains unknown.
Hypothesis: We hypothesized that FVC fall at PC20 during a methacholine challenge was increased in overweight and obese patients with asthma-like symptoms.
Methods: 298 consecutive adult women with asthma-like symptoms underwent a methacholine bronchial provocation test according to ATS-guidelines. PC20 methacholine and FVC fall at PC20 were computed for all subjects. Bronchial Hyper-Responsiveness (BHR) was considered when PC20 was ≤1600μg. PC15 and FVC fall at PC15 were recorded in patients who did not achieve a 20% fall of Forced Expiratory Volume in 1 second (FEV1s).
Results: A logistic regression with age, smoking and Body Mass Index showed that only obesity (BMI ≥ 30) increased the risk of BHR with an odds-ratio of 4.2 (95 CI: 1.670–12.295) (p=0.0041). BMI had no impact on the relationship between FEV1s and FVC (p=0.2490). On the other hand, BMI influenced the percentage fall in FVC at the PC15 only in patients with PC20>1600μg (normal 9±13%; overweight 10±16% and obese 15±32%, p=0.0073).
Conclusion: Obesity is a risk factor for BHR in women patients with asthma symptoms. FVC fall at PC20 is not affected by the BMI. Nonetheless, in obese women with asthma symptoms but negative methacholine challenge, we observed a potential involvement of distal airways measured by the FVC.
- © 2011 ERS