Background: The carbon footprint of severe asthma and the impact of biologic therapy in this population is unknown.
Methods: This was a retrospective cohort study in adults with severe asthma, using data from the Northern Ireland Regional Severe Asthma Service (September 2015-November 2021). We calculated annual greenhouse gas (GHG) emissions (carbon dioxide equivalent) for asthma-related medications and healthcare resource utilisation, compared patient characteristics by GHG quartile, calculated GHG change post-biologic initiation, and explored the relationship between GHG change and clinical response.
Results: Among 303 patients with severe asthma, mean±sd GHG emissions were 474±431 kg, largely driven by SABA use (50.7%) and emergency department (ED) visits/inpatient admissions (21.0%). Those with highest-quartile GHG emissions were more likely to have uncontrolled disease (Asthma Control Questionnaire-5 score 3.5 versus 2.5; p<0.001), be more deprived (46.1% versus 25.0%; p=0.029) and have depression/anxiety (35.5% versus 14.7%; p=0.002) versus those with lowest-quartile GHG emissions. Among patients who received a biologic (n=213), modest GHG reductions (-28.0±286 kg; p=0.15) were observed, largely driven by a reduction in ED/hospitalisation-related GHG emissions (-59.3±224 kg; p<0.001). SABA-related GHG emissions were relatively unchanged (-6.1±138 kg; p=0.518). Total GHG emissions were 72.4±352 kg (p=0.044) lower than baseline at 4 years post-biologic initiation. Although there was substantial clinical improvement post-biologic initiation, this was not associated with GHG reductions.
Conclusions: Severe asthma is associated with substantial GHG emissions, primarily driven by SABA use and emergency care utilisation. Although GHG emissions were lower post-biologic, largely due to a reduction in emergency care, the changes in GHG emissions were modest and SABA use was relatively unchanged. An improved understanding of the factors driving elevated GHG emissions is required.
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