Introduction: Asthma management contributes significantly to healthcare carbon footprints. We wanted to find out if as-needed budesonide-formoterol via a dry powder inhaler (DPI) was associated with a reduction in carbon footprint compared with as-needed salbutamol pressurised metered-dose inhaler (pMDI)-based therapies in mild asthma.

Methods: This post hoc analysis included all 668 participants in the Novel START study, who were randomised 1:1:1 to treatment with: as-needed budesonide-formoterol DPI, as-needed salbutamol pMDI, or maintenance budesonide DPI plus as-needed salbutamol pMDI. The primary outcome was the carbon footprint of asthma management (inhalers and healthcare encounters for asthma exacerbations), expressed as kilograms of carbon dioxide-equivalent (Kg CO2e), per person year.

Results: As-needed budesonide-formoterol DPI was associated with 95.8% and 93.6% reductions in carbon footprint compared with as-needed salbutamol pMDI (least squares mean 1.1 vs 26.2 Kg CO2e; difference -25.0, 95%CI -29.7 to -20.4; P<0.001) and maintenance budesonide DPI plus as-needed salbutamol pMDI (least squares mean 1.1 vs 17.3 Kg CO2e; difference -16.2, 95% CI -20.9 to -11.6; P<0.001), respectively.

Conclusions: As-needed budesonide-formoterol DPI was associated with a marked reduction in carbon footprint compared with as-needed salbutamol pMDI and compared with maintenance budesonide DPI plus as-needed salbutamol pMDI.