Summary Background Several observational studies have demonstrated an association between obesity and asthma. Studies evaluating exhaled nitric oxide levels and obesity have revealed that a higher body mass index (BMI) is associated with elevated exhaled nitric oxide levels. Airway inflammation using sputum cell counts has not been assessed in obese patients with airway diseases. Objective The primary aim of this study was to determine whether obesity (based on BMI) is associated with eosinophilic or neutrophilic bronchitis. Methods The results from a database of induced sputum cell counts were compared with BMI and analysed using correlation statistics, regression and parametric and non‐parametric analysis. Results Seven‐hundred and twenty‐seven adult participants with an equal number of sputum samples were included in the analysis. BMI varied from 14.5 to 55 kg/m2. Sputum total cell count (mean±SD: 12.9 × 106 cell/g±21.5), eosinophil percent (median; min to max: 0.3%; 0–89.0), and neutrophil percent (mean±SD: 63.5±26.6%) were within normal limits. Participants with asthma had a higher percentage of sputum eosinophils than those without asthma (P=0.01). However, there was no difference in the total or differential cell counts among the obese and non‐obese participants, when the data were analysed according to BMI category, gender, dose of inhaled corticosteroid, and presence or absence of asthma. Conclusion In this large sample of adult asthmatic and non‐asthmatic participants, there was no association between BMI and airway inflammation measured by sputum cell counts. Other mechanisms to explain the relationship between obesity and asthma will need to be explored if this association is to be better understood.

There is heterogeneity in the cellularity of sputum in various airway diseases. Patients with clinically stable airway diseases may have high sputum cell counts. During exacerbations, more patients may experience neutrophilic bronchitis. Severity of airflow obstruction is associated with eosinophilic bronchitis in patients with asthma, and neutrophilic bronchitis in patients with nonasthmatic COPD.

BackgroundPatients with symptoms of both asthma and chronic obstructive pulmonary disease (COPD) may be classified with the term asthma-COPD overlap (ACO). ACO is of considerable interest as it is currently poorly characterised and has been associated with worse health outcomes and higher healthcare costs compared with COPD or asthma alone. Patients with ACO in Asia remain poorly described, and there is limited information regarding their resource utilisation compared with patients with asthma or COPD only. This study investigated the characteristics, disease burden and medical resource utilisation of patients with ACO in Taiwan.MethodsThis was a retrospective cohort study of patients identified from National Health Insurance (NHI) claims data in Taiwan in 2009–2011. Patients were classified into incident ACO, COPD or asthma cohorts according to International Classification of Disease, ninth revision, clinical modification codes in claims. Eligible patients were ≥40 years of age with 12 months’ continuous enrolment in the NHI programme pre- and post-index date (date of the first relevant medical claim).ResultsPatients with ACO (N = 22,328) and COPD (N = 69,648) were older and more likely to be male than those with asthma (N = 50,293). Patients with ACO had more comorbidities and exacerbations, with higher medication use: short-acting β2-agonist prescriptions ranged from 30.4% of patients (asthma cohort) to 43.6% (ACO cohort), and inhaled corticosteroid/long-acting β2-agonist combination prescriptions ranged from 11.1% (COPD cohort) to 35.0% (ACO cohort) in the 12 months following index. Patients with ACO generally had the highest medication costs of any cohort (long-acting muscarinic antagonist costs ranged from $227/patient [asthma cohort] to $349/patient [ACO cohort]); they also experienced more respiratory-related hospital visits than patients with asthma or COPD (mean outpatient/inpatient visits per patient post-index: 9.1/1.9 [ACO cohort] vs 5.7/1.4 [asthma cohort] and 6.4/1.7 [COPD cohort]).ConclusionsPatients with ACO in Taiwan experience a greater disease burden with greater healthcare resource utilisation, and higher costs, than patients with asthma or COPD alone.Electronic supplementary materialThe online version of this article (10.1186/s12890-017-0571-7) contains supplementary material, which is available to authorized users.