Around 5.4 million people are treated for asthma in the UK. Asthma is treated with inhaled medication; patients can use a 'reliever inhaler' for immediate symptom-relief, and/or a 'preventative inhaler' to prevent asthma symptoms occurring. All reliever inhalers in the UK contain a type of drug called a short acting beta-agonists (SABA). All preventative drug regimens should contain an inhaled steroid (ICS). Clinical guidelines inform how and when inhalers should be used; for example, a patient with mild asthma may only use SABA, or only use SABA and low dose ICS, but a patient with moderate disease may use SABA and high dose ICS (as well as other medications). The clinical guidelines specify that a patient should have optimal asthma control (no asthma symptoms) and that a sign that they do not is if they are using their SABA inhaler more than twice a week; if a patient is using SABA frequently, it is likely that they should be on a higher ICS doses. Therefore this study aims to, firstly, describe the SABA and ICS inhaler prescription patterns in the UK over the past decade, and secondly, the effect these inhalers on asthma health outcomes and asthma-related healthcare resource utilisation.
Finally, we will estimate the cost of SABA use in the UK from an economic and environmental perspective. The economic burden for society in the UK is currently very high. In addition to direct costs, there is also a high environmental impact regarding greenhouse gas (GHG) emissions. SABA inhaler over-use, and asthma related health-care utilisation due to exacerbations contribute to both and will be studied in order to better understand total costs incurred.
We will describe the UK’s current asthma population in terms of its SABA and ICS prescriptions, and temporal patterns (dataset=all eligible current asthma patients in CPRD). Patients will be categorised according to their SABA and ICS use in terms of British asthma guidelines. We will describe the demographic characteristics, asthma-related characteristics, treatment patterns, and exacerbations by BTS/GINA step and prescription coverage of ICS prescriptions. We will use a cohort study design to compare the effects of different patterns of SABA prescriptions on health outcomes (main outcome=exacerbations; using Cox and negative binomial models), healthcare resource utilisation (main outcome=GP visits; using Poisson or negative binomial models, depending on distribution) (dataset=all eligible current asthma patients in CPRD that are linked with HES-ONS, for exacerbations, or not linked for healthcare resource), and cost (financial and environmental; using negative binomial model in HES-linked data). SABA prescriptions will be the main exposure, derived from 12 months of prescription data before the study start, both as categorical and continuous. Models will be adjusted for multiple potential confounders, including ICS prescriptions. If the descriptive analysis shows patients change between exposure categories over time then this will be taken into account by censoring patients when they change exposure category, and in sensitivity analyses, by taking into account the time-varying exposures.
Health Outcomes to be Measured:
- Asthma control
- Asthma-related health resource use
- Asthma medication use
- All-cause Mortality
- Asthmas-specific mortality
HES Accident and Emergency;HES Admitted Patient Care;HES Outpatient;ONS Death Registration Data;Practice Level Index of Multiple Deprivation