Exploring the carbon footprint of severe asthma and change after biologic therapy initiation: an analysis of Northern Irish data

Introduction: The carbon footprint of severe asthma (SA) and the impact of biologic therapy in this population is unknown.

Methods: This was a retrospective cohort study in adults with SA, using data from the Northern Ireland Regional Severe Asthma Service (September 2015-November 2021). We calculated annual greenhouse gas emissions (GHGs; 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 SA, mean GHGs was 474kg (SD:431), largely driven by SABA-use (50.7%) and ED/hospitalizations (21.0%). Those with highest-quartile GHGs were more likely to have uncontrolled disease (ACQ 3.5 vs 2.5; p<0.001), be more deprived (46.1% vs. 25.0%, p=0.029) and have depression/anxiety (35.5% vs. 14.7%, p=0.002) versus those with lowest-quartile GHGs. Among patients who received a biologic (n=213), modest GHG reductions (-28.0kg [SD:286], p=0.15) were observed, largely driven by reduction in ED/hospitalization-related GHGs (-59.3 [SD:224], p<0.001). SABA-related GHG emissions were relatively unchanged (-6.1 kg [SD:138]), p=0.518). Total GHGs were 72.4kg (SD:352, p=0.044) lower than baseline 4-years post-biologic-initiation. Although there was substantial clinical improvement post-biologic-initiation, this was not associated with GHG reductions.

Conclusions: SA is associated with substantial GHGs, 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 GHGs were modest and SABA-use was relatively unchanged. An improved understanding of the factors driving elevated GHGs is required.