Relationship between asthma, obesity and other comorbidities: the Australasian Severe Asthma Registry

Background The impact of obesity and sex on asthma outcomes and inflammation in the real-world setting is not completely understood. The aim of this study was to profile obesity and other comorbidities in a cohort of male and female adults with asthma; to understand the impact of obesity on asthma outcomes; and to examine sex-specific relationships between obesity and airway inflammation. Methods We profiled comorbidities including obesity, as well as clinical asthma outcomes and airway inflammation, in patients with asthma enrolled in the Australasian Severe Asthma Registry. Data were analysed using t -tests (parametric data) or Wilcoxon rank sum tests (non-parametric data). Analysis of covariance (ANCOVA) was used to examine the effects of obesity and asthma severity on clinical and inflammatory outcomes. Results We assessed 1,019 patients with severe ( n = 882) and non-severe ( n = 137) asthma. Patients with severe asthma were 67% more likely to have obesity, while patients with severe asthma and obesity were more likely to be female. Obesity was associated with a higher prevalence of asthma-related hospitalisation in the previous 12 months, in both severe (26.2% vs. 15.7%, p < 0.001) and non-severe asthma (12.5% vs. 3.1%, p < 0.001). Obesity was also associated with poorer asthma control and lung function, and higher sputum neutrophils. Interestingly, sputum %neutrophils correlated with body mass index in females ( r s =0.370, p = 0.003), but not males ( r s =0.092, p = 0.495). Neutrophilic airway inflammation was associated with poorer lung function and asthma control. Conclusions This study demonstrates that obesity is associated with a significantly worse clinical asthma presentation in the real-world setting and increases the risk of asthma-related hospitalisation. Critically, our findings suggest that obesity is associated with increased neutrophilic airway inflammation in females, but not males, providing some insight into possible sex-related differences in severe asthma.