Obesity associated severe asthma represents a distinct clinical phenotype - Analysis of the British Thoracic Society Difficult Asthma Registry patient cohort according to body mass index.
Chest. 2012 Oct 8. doi: 10.1378/chest.12-0872. Gibeon13 D, Batuwita2 R, Osmond2 M, Heaney4 LG, Brightling5 CE, Niven6 RM, Mansur7 AH, Chaudhuri8 R, Bucknall9 CE, Rowe2 A, Guo2 YK, Bhavsar3 PK, Chung13 KF, Menzies-Gow1 AN.
BACKGROUND: Obesity has emerged as a risk factor for the development of asthma and it may also influence asthma control and airways inflammation. However, the role of obesity in severe asthma remains unclear.
OBJECTIVE: To explore the association between obesity (defined by BMI) and severe asthma.
METHODS: Data from the National Registry for dedicated UK Difficult Asthma Services were used to compare patient demographics, disease characteristics and healthcare utilisation between three body mass index (BMI) categories (normal weight: 18.5 -24.99, overweight: 25 -29.99, obese: ≥30) in a well characterised group of severe asthmatic adults.
RESULTS: The study population consisted of 666 severe asthmatics with a median BMI of 29.8 (interquartile range 22.5 -34.0). The obese group exhibited greater asthma medication requirements in terms of maintenance corticosteroid therapy (48.9% versus 40.4% and 34.5% in the overweight and normal weight groups, respectively), steroid burst therapy and short-acting β2-agonist (SABA) use per day. Significant differences were seen with gastro-oesophageal reflux disease (GORD) (53.9% versus 48.1% and 39.7% in the overweight and normal weight groups, respectively) and proton pump inhibitor (PPI) use. Bone density scores were higher in the obese group, whilst pulmonary function testing revealed a reduced FVC and raised Kco. Serum IgE levels decreased with increasing BMI and the obese group were more likely to report eczema, but less likely to have a history of nasal polyps.
CONCLUSIONS: Severe asthmatics display particular characteristics according to BMI that support the view that obesity associated severe asthma may represent a distinct clinical phenotype