In this real-world, observational study, high SABA inhaler use was prevalent in over one-third of UK patients with asthma. High SABA users were significantly more likely to have exacerbations than low SABA users, even after considering multiple known exacerbation risk factors, in patients across BTS steps. High SABA users were also significantly more likely to attend primary care consultations and consultations with a specialist, regardless of asthma severity.
Consistent with previous UK data , the majority of patients (65%) received BTS steps 1/2 treatment and may be considered to have mild asthma. Notably, over half of the patients were managed on BTS step 1 treatment. While the BTS guidelines are used across the UK, both BTS and GINA recommend a stepwise approach to the pharmacological treatment of asthma and until recently , GINA recommended a similar management approach for patients with mild asthma . However, the 2019 GINA report saw a fundamental change, recommending that step 1 treatment is no longer SABA alone but includes low-dose ICS-formoterol as a preferred reliever . Our study found that even mild asthma patients experienced exacerbations, in keeping with previous findings [5, 6, 26, 33,34,35], and that this risk appeared to be further elevated with high SABA use. This analysis points to an association but not a causal relationship between over-reliance on SABA inhalers and poor clinical outcomes in patients with mild asthma. This evidence of an association even while adjusting for confounding factors, such as exacerbation history (potentially indicating poor control), ICS dose, and PDC (in BTS step 2 patients), indicates that high use of SABA inhalers, in part, may contribute to poor clinical outcomes in this subset of patients. These real-world findings therefore appear to support the concept of treating mild asthma patients with anti-inflammatory medications and not just a short-acting bronchodilator alone.
A significant dose–response effect of increased exacerbation risk with increasing SABA inhaler use was seen across severities. SABA inhaler use, from as few as 2 canisters/year in patients receiving BTS steps 3–5 treatment (and thus potentially having moderate-to-severe asthma), was a significant risk factor for exacerbations even after considering disease severity and multiple other known risk factors. Earlier observational studies addressing concerns related to SABA use have reported similar results, but the studies have only focused on hospitalized exacerbations [15,16,17, 36]. In contrast, our study addressed exacerbations managed within primary and secondary care.
The largest study preceding this one was carried out in a Canadian population, which used administrative data to evaluate the risk of SABA use on hospitalizations . They found an increase in hospitalizations, but the question remained whether the increases observed were related to the financial barriers faced by some Canadian patients due to incomplete publicly administered medication coverage. Similarly, a previous study conducted in the United States, which also used administrative data, found considerable increments in total healthcare costs with increasing SABA use, posing the same question about the impact of financial barriers . This UK study, evaluating the impact in a population with complete medication coverage, has shown that the association between high SABA use and adverse asthma outcomes and healthcare utilization is not related to financial barriers.
Notably, these results highlight high SABA use and associated burden even in patients with mild asthma. Whether the healthcare utilization burden associated with high SABA use is due to patients having poor asthma control, or whether this represents actual burden associated with high SABA use itself, will require further investigation. It is possible that increased SABA inhaler use is preceded by the deterioration of asthma control and is reflected by an increase in patient’s symptoms. Asthma control was not specifically adjusted for in this analysis; however, exacerbation history was one of the confounding factors, which may indirectly reflect asthma control. Of note, assessment of qualitative research focusing on patient-centered drivers of poor medication adherence suggests that SABA overuse may not always be related to the severity of the disease. It may also be due to factors including ICS underuse driven by suboptimal patient knowledge about the difference between maintenance and reliever medication, the patient’s need for immediate symptom relief, concerns about the side-effects of steroids, and poor communication between patients and physicians . Additionally, previous analysis of the same patient cohort revealed that, over an 8-year period, SABA prescriptions at the population-level have remained stable . However, there was greater variability year to year in prescriptions of SABA compared with ICS, suggesting that SABA use, rather than ICS use, may be altered in response to changes in asthma control . Overall, these findings indicate a need for outreach strategies involving medical education targeted at patients, healthcare providers, and policymakers, and digital health initiatives (e.g., digital inhalers) [39, 40], in order to align SABA prescription behavior with current treatment recommendations.
The use of the CPRD has several limitations. Prescriptions recorded in the database did not necessarily represent dispensed or used inhalers, potentially leading to an overestimation of actual SABA inhaler use. The baseline BTS step was used to represent severity throughout follow-up, and it is possible that this changed over time. Additionally, many patients on step 1 treatment did not receive a SABA prescription in the baseline year and therefore potentially did not have active asthma. However, sensitivity analyses excluding these patients did not yield a change in effect estimates (Table S3), and 91% received asthma management in the year before or after the baseline year. It is possible that the remaining 9% were in remission, misdiagnosed, or did not wish to receive treatment for their asthma during the 3-year period. The outcomes cohort (requiring patients only with HES linkage) constituted approximately 60% of the total asthma patients eligible for the prescription analysis; this could lead to a selection bias, although HES has universal coverage of English hospitals, thus providing an unselected sample . In most countries including the UK, SABA inhalers contain 100 or 200 puffs. However, in order to standardize the threshold for high SABA use across countries in the SABINA program, a SABA inhaler was considered to contain an assumed average of 150 puffs. Nebulized SABA use was not analyzed separately; however, it is not commonly prescribed in the UK, except for more severe asthma patients , and is recommended for the treatment of acute severe asthma attacks in children by paramedics or in the A&E .
Limited data on the burden of high SABA use and considerable variability in the definition of SABA ‘overuse’ [17, 43,44,45] have made comparisons with previous studies and regions challenging. In the SABINA program , the definition of high SABA use has been standardized across studies, enabling comparison and harmonization of results across geographies. Emerging data from more than 1 million patients in the SABINA program reveal that high SABA use is also prevalent in other European countries, such as Sweden (30%), Germany (16%), Spain (29%), and Italy (9%), and is found across asthma severities . Moreover, the HERA study, conducted in a Swedish asthma cohort as part of the SABINA program, showed similar results: among high SABA users, constituting one-third of all asthma patients, the risk of exacerbations and asthma-related mortality significantly increased with use of ≥ 3 SABA canisters/year . The current study describes SABA inhaler use in more than half a million asthma patients, allowing for characterization of exacerbation rates and healthcare utilization across all asthma severities. Furthermore, patients in CPRD are nationally representative in terms of age, sex, and BMI , ensuring that the results of this study are generalizable to the national population. Additionally, in the UK healthcare system, all patients are assigned to a GP and most prescriptions are undertaken in primary care, as GPs are in a good position to provide continuing care. Thus, these findings on SABA inhaler prescription patterns are representative of the entire UK asthma patient population.