Introduction

Inhalers are essential treatments for asthma and COPD but contribute to healthcare carbon emissions, particularly pressurized metered‑dose inhalers (pMDIs) that release hydrofluoroalkanes. These inhalers account for about 22% of primary care’s carbon footprint (CF), while dry powder inhalers (DPIs) can reduce emissions substantially. Global Initiative for Asthma (GINA) recommends Track-1 asthma therapy with inhaled corticosteroid (ICS)–formoterol (FOR) as a single maintenance and reliever therapy (SMART). GINA also recommends ICS plus short‑acting beta‑agonist (SABA) as an alternative Track‑2 approach. However, the long-term health outcomes and CF of different inhaler strategies in Singapore’s primary care system remain uncertain.

Aim

To compare asthma control and carbon footprints among adult asthma patients treated with budesonide‑formoterol (BUD-FOR) DPI alone (Track-1) vs BUD-FOR DPI plus SABA-pMDI as a reliever therapy (Track-2).

Method

Study Design

Patient Profile 

• Patients aged >21 years with clinical diagnosis of asthma 
• Having atleast 1 asthma control test (ACT) score per year

Data Management and Analyses 

• Electronic medical records from eight public primary care clinics were analysed for adult asthma patients aged 21 and above between 2018 and 2023
• Data included inhaler dispensing records, ACT scores, and rescue therapy (RT) requirements
• CF was calculated based on the number and type of inhaler canisters dispensed
• Associations between treatment modality, asthma control, RT use, and CF were assessed using generalized estimating equations (GEE)

Endpoints

• Inhaler utilization (number of canisters dispensed)
• Asthma control based on ACT scores
• Carbon footprint 
• Need for rescue therapy

Results

• The study included a total of 5634 patients using BUD-FOR DPI
• The usage of Track-1 increased substantially from 466 to 2317 patients, while the usage of Track-2 rose modestly from 628 to 758, over the study period
• Good asthma control (ACT ≥20) was achieved by 78.5% in Track-1 cohort in 2023, compared to 68.7% in Track-2 cohort
• Track-1 usage was associated with lower total CF per patient vs Track-2 usage (3.3 vs 62.4 kgCO₂e)
• Patients in Track-1 had a substantially lower CF by 60 kgCO₂e (p<0.001)
• GEE analysis revealed that patients on Track-1 had 1.5 times likelihood of achieving good asthma control (p<0.001) and had approximately 30% lower odds of receiving RT; p<0.001
• The average number of SABA-pMDI canisters dispensed per patient declined from 2.8 to 2.1 over the study period
• The number of BUD/FOR inhalers dispensed per patients per year was consistently higher in Track 2 compared to Track 1, with an average difference of 1.2 canisters (5.3 vs 4.1)

Conclusion

• Patients treated with the Track‑1 modality achieved better asthma control and had a substantially lower carbon footprint than those on Track‑2 therapy. 
• Clinicians should consider wider adoption of Track‑1 due to its superior clinical effectiveness and environmental benefits, while actively educating and engaging patients to support shared, informed decisions when transitioning therapies.

J Prim Care Community Health. 2026 Feb 14;17:21501319251411430.   Doi: 10.1177/21501319251411430