Abstract
Patients are using more inhaled corticosteroids (ICS)-long-acting β2-agonist (LABA), with add-on short-acting β2-agonist (SABA) as reliever based on guidelines. The ICS-LABA inhalers are available in Singapore in either pressurized metered-dose (pMDI) or dry-power (DPI) inhalers. Both generate carbon emissions. This retrospective study aimed to determine the asthma control and quantify the carbon emissions resulting from the use of ICS-LABA inhalers by adults who were managed in primary care and comparing them between those with good versus suboptimal asthma control. Data of Asian patients aged >=21 years with a clinical diagnosis of asthma were extracted from their electronic medical records in nine Singapore primary care clinics from 2015-2023, including their demography, clinical diagnoses, asthma control test (ACT) scores and medications dispensed from in-house pharmacies. ACT ≥ 20 is regarded as good asthma control. The total carbon emissions from ICS-LABA and SABA (pMDI or DPI) were calculated respectively. Patients using ICS-LABA increased from 2021 (2015) to 6606 (2023); those with well-controlled asthma rose from 57.1-75.9%. Total carbon emissions increased from 106,871-367,832 kg CO2e/year and from 361,335 (2015) to 797,016 (2023) kg CO2e/year for ICS-LABA and ICS-LABA+SABA respectively. Each patient emitted average of 120.7 kg CO2e/year from ICS-LABA+SABA in 2023, a decline from 178.8 kg CO2e in 2015. Patients with suboptimal asthma control had significantly higher carbon emissions by 35 kg CO2e/year compared to those with good control (p < 0.001). More patients were treated with ICS-LABA from 2015-2023, but their total carbon emissions declined with better asthma control and reduced SABA usage.