Overweight is associated with airflow obstruction and poor disease control but not with exhaled nitric oxide change in an asthmatic population

Background: The role of an elevated body mass index (BMI) in asthma remains controversial.

Objectives: To investigate the relationship between overweight (BMI >25 and ≤30), lung function, disease control, and airway inflammation in an asthmatic population.

Methods: We consecutively studied 348 patients (age 43 ± 16 years; 211 females). In all patients, BMI, spirometry, the Asthma Control Test (ACT), and fractional exhaled nitric oxide (FeNO; ppb) were measured.

Results: One hundred forty-five patients were overweight and, as compared to those with normal BMI, had lower values of FVC, FEV(1), and FEV(1)/FVC and of FEF(25-75) even when normalized for FVC (p < 0.05 for each comparison). The ratio between the number of patients with well-controlled asthma (ACT ≥20) and that of patients with poorly controlled asthma (ACT < 20) was significantly lower in overweight patients (1.07 vs. 1.84; χ(2) = 6.030, p < 0.01). In overweight patients, the odds ratio of uncontrolled asthma expressed by logistic regression analysis was 1.632 (95% CI = 1.043-2.553), independently of gender, atopy, smoking habit, and inhaled steroid therapy. No difference was observed in FeNO values between overweight and normal weight patients (27.7 ± 2.3 vs. 27.9 ± 2.2 ppb).

Conclusions: Our results show that, in an asthmatic population, overweight is associated with airflow obstruction and poor disease control but not with FeNO change. The findings of the present study support the view that other factors besides airway inflammation alone may explain the relationship between asthma and an elevated BMI.