Discussion
Our analysis shows that considerable carbon savings can be achieved by addressing three major aspects of care in asthma and COPD: misdiagnosis, suboptimal symptom control, and prominent use of strategies featuring MDI prescriptions.
Given that only 48% and 36% of patients with a clinical diagnosis of asthma or COPD, respectively, are sent for confirmatory objective testing,38 39 many patients carrying this label do not in fact have the disease. In addition to the substantial carbon savings that we have demonstrated, addressing this misdiagnosis in asthma and COPD will benefit health systems and patients alike by decreasing unnecessary medication use and corresponding costs and side-effects, and by reducing delays in identifying the actual diagnosis in misdiagnosed patients.40 Although carbon savings achieved by addressing mis/overdiagnosis have been considered in other diseases,41 we are not aware of comparable analyses in airways diseases. However, we do note that significant ‘underdiagnosis’ also exists, with 20–70% of patients with asthma42 and up to 70% of patients with COPD in the community being undiagnosed.43 Accordingly, approaches to improve availability and uptake of objective testing will also likely drive increased appropriate diagnoses and corresponding treatment. Although this will improve patient outcomes, it will decrease carbon savings achieved through reduced misdiagnosis. However, if previously undiagnosed patients are managed according to guideline criteria to achieve good disease control and are preferentially prescribed DPI inhalers (the other two analysed strategies), the environmental impact of new diagnoses will be minimal.
Over half of patients with asthma44–46 and COPD47 do not meet guideline criteria for well-controlled disease. Multiple criteria are considered when defining disease control,29 48 In asthma, the most common reason for a poor control status is a high acute symptom burden requiring frequent rescue therapy,25 while in COPD, exertional dyspnoea and overall disability seem to drive overuse.28 In addition to expected improvements in health and healthcare system burden, our analysis demonstrates that improving disease control reduces the carbon footprint associated with both asthma and COPD.49 Previous authors have suggested comparable carbon savings with such an approach using European market share data.5 50 Ultimately, markets in which MDIs dominate SABA prescriptions, such as the US,18 the UK19 and Canada,20 or where SABA excess use is more prevalent51 will realise the greatest GHG emission reductions from therapeutic optimisation. Although escalation of controller therapy will be required to achieve control in most patients, non-pharmacological interventions remain an underused but important aspect of care that will also reduce rescue inhaler use and corresponding GHG emissions (see Solutions, below). It is also of note that in improving disease control, not only would emissions from day-to-day rescue inhaler use be reduced, but also those associated with exacerbation care (estimated at ~700 000 MT CO2e a year in the UK alone).49
Over the years, despite the availability of propellant-free devices (eg, DPIs), MDIs have remained the most widely used delivery system for short-acting relievers (>90% of inhalers sold),5 as well as for ICSs and ICS/LABAs (about half of inhalers sold), despite multiple DPI options in these classes.20 Our study expands on previous findings suggesting that switching MDIs to DPIs could offer attractive carbon savings in asthma and COPD.5 7 50 52 53 Janson et al5 reported that switching 80% of Salbutamol MDIs to DPIs would save 550 000 MT CO2e annually in the UK. Although we used a more conservative 25% estimate, per capita GHG savings estimates were similar in our study. It is of note, however, that this benefit will be attenuated in markets where DPIs already have a larger market share (eg, Sweden).19 Although concerns arise about higher costs of DPIs, Wilkinson et al54 showed that drug costs can actually decrease when selecting the lowest cost DPI within the same drug class. In a global analysis, Kponee-Shovein et al55 calculated that substituting 2–5% of MDIs with DPIs annually would result in inhaler GHG emission reductions by 38–58% over 50 years, with only slightly increased costs. While the impact of switching devices on asthma control might also be of concern for clinicians, one study showed that changing prescriptions from MDIs to DPIs for the same molecule succeeded in significantly reducing the carbon footprint associated with therapy without loss of control.53 We also show that favouring budesonide/formoterol DPI rescue and maintenance therapy56 (in mild asthma) and combining separate inhalers into a single triple therapy combination inhaler (in COPD) in some patients can drive further GHG emission reductions. Each of these approaches is preferred by patients57 58 and increases adherence.59 Finally, even switching within MDIs can sometimes be beneficial. Controller MDIs using an HFC-227ea propellant carry a global warming potential that is 2.65 times higher than those using an HFC-134a propellant.27 Similarly, some SABA MDIs use ethanol and/or oleic acid to reduce the amount of propellant required,27 providing a lower GHG-emitting option within the SABA MDI class. Given that about 5% of patients struggle to use DPIs60 and that some prefer MDIs,61 we identified sizeable carbon savings achievable simply by switching some patients to lower GHG-emitting MDIs. Of note, HFC-152a—a new propellant expected to enter the market in 2025—may enable a 90% emission reduction in each actuation (as compared with HFC-134a, used in most MDIs),7 50 highlighting that future innovations present opportunities for even greater impact.
Solutions
Several strategies can be implemented to address the three analysed aspects of care responsible for avoidable GHG emissions in asthma and COPD.
Improving diagnosis
Addressing misdiagnosis in asthma and COPD requires increased use of objective pulmonary function testing, particularly in primary care, where the majority of such patients are managed.62 A recent systematic review applied the Theoretical Domains Framework to identify barriers and enablers to use of spirometry in suspected asthma and/or COPD in primary care settings.63 Matching these determinants to corresponding behaviour change techniques, they suggested that interventions with the following components could be effective in this setting: electronic-medical record-embedded prompts for objective testing; improved remuneration for spirometry performance and interpretation in office settings; improved access (decreased wait times and travel distances) to spirometry in laboratory settings; audit and feedback on provider performance; and provider education regarding the inaccuracy of clinical diagnosis. The carbon footprint savings identified in our analysis could also be included in such educational content, as environmental stewardship is a potent motivator for change in primary care practice.64
Improving symptom control
Improvements in symptom control in order to reduce rescue inhaler use may be achieved through both provider-facing and patient-facing interventions. Studies show that primary care providers do not routinely assess their patients’ asthma control, leading to under-recognition of poor control and corresponding under-prescription of controller medications.65 66 Over two-thirds of patients with poorly controlled asthma have not been prescribed first-line or second-line controller therapies,45 66 and when they do escalate therapy, providers do not follow guideline recommendations in a majority of cases.46 In COPD, assessments of dyspnoea, impact of symptoms on daily life and risk of future acute exacerbations—which should guide pharmacotherapy—are seldom performed in practice,67–69 leading to both under-prescription of long-acting bronchodilators and over-prescription of ICSs.70–72 In both diseases, lack of symptom assessment also results in missed opportunities for therapeutic de-escalation in well-controlled patients (which in some cases, would reduce GHG emissions). These gaps are driven by multiple barriers including a lack of knowledge of disease control parameters,73–75 lack of time to assess control74 and lack of familiarity with what is often rapidly changing guidance.74 76 Accordingly, strategies to improve treatment will be necessarily complex and multifaceted. Recently, a technology-based intervention that includes a patient-facing questionnaire linked to a computerised decision support system for primary care providers improved both assessment of control and prescription of controller therapies.77 Successful strategies such as this require adaptation for COPD and scaling across health systems.
Even when providers prescribe appropriate controller therapies, patient disease management knowledge78–80 and treatment adherence remain low.81 Self-management interventions including education, regular practitioner review and a written self-management action plan, as well as patient decision aids82 have been shown to improve adherence,83 84 leading to reduced requirements for rescue therapy in asthma and COPD.82 85 Effective delivery of such educational interventions across health systems will require a commitment to train and fund multidisciplinary personnel with required expertise.86
Optimising therapeutic choice
Carbon savings through preferential use of DPIs (or lower GHG-emitting MDIs) over conventional MDIs can be realised by selecting the preferred device at the time of initial prescription, through strategies such as provider education and default choices in electronic medical record systems.87 Although switching patients on established therapy to new devices may also be considered, this may affect medication self-efficacy and adherence, and increases the risk of administration errors88 and loss of symptom control,89 paradoxically increasing emissions due to acute care events (which are highly carbon-intensive).49 Accordingly, therapeutic switches must be paired with proper device education.90 91 Here, pharmacist-led education has been shown to improve technique,92 93 and new device technologies providing real-time patient feedback present a promising adjunct.94 It is of note, however, that about 5% of patients demonstrate insufficient inspiratory effort to adequately use a DPI (note that in some reports up to one-third of patients did not adequately use an MDI).60 Also, DPIs require coordination of respiratory efforts that may be challenging for children aged 6 or under,56 and many patients simply prefer MDIs.95 Accordingly, device selection should be individualised. Although unconsented switches should not be considered, in patients who want to discuss different inhaler options, clinicians could present a range of options along with information about their differing environmental impacts (an aspect that >80% of patients value),96 in order to reach a shared treatment decision.82 The same approaches could be used to drive use of therapeutic strategies featuring combination inhalers rather than separate inhalers, also driving carbon savings. In fact, decision aids addressing some of these shared decisions already exist. The British National Institute for Health and Care Excellence produced a decision aid that compares inhalation manoeuvre requirements and carbon footprint between MDI and DPI devices.97 In mild asthma, an electronic decision aid and conversation aid address the choice between (separate) ICS+SABA inhalers and as-needed budesonide/formoterol DPI.98 Herein, we present a one-page conversation aid for choosing a reliever inhaler in patients with mild asthma, adding to existing tools by including comparisons between high-GHG-emitting and low-GHG-emitting MDI devices, treatment costs96 98 and device disposal considerations (figure 3) (also see online supplemental material S2).
Figure 3An in-office conversation aid to support patients with mild asthma in choosing their rescue inhaler.
This conversation aid can be used to arrive at a shared decision between patients and providers surrounding selection of a rescue inhaler device.
Limitations
Our analysis has several limitations. First, in our calculations, we used life-cycle assessment GHG emissions that are comprised of emissions from the production, use and the end-of-life disposal of the device, and emissions from the propellant (for MDIs). However, our calculations do not consider emissions associated with the active pharmaceutical ingredient in each device,99 whereby actual inhaler GHG emissions for all devices are higher than reported. Second, avoidable GHG emissions from misdiagnosis may be slightly overestimated due to the fact that a small proportion of patients misdiagnosed with asthma could in fact have COPD,22 and vice-versa. Third, carbon savings achieved by the three main approaches suggested are not necessarily additive. For example, reductions in MDI use through improved diagnosis and disease control would limit additional emission reductions achievable through MDI to DPI substitutions. We attempted to account for this by considering carbon savings from only 25% of devices being substituted. Similarly, if patients with mild asthma preferentially receive as-needed budesonide/formoterol DPI rather than ICS+SABA therapy, GHG emission reductions that would otherwise have been achieved through improved diagnosis and disease control would be reduced. A similar effect would be seen if there was broad use of maintenance and reliever therapy with budesonide/formoterol DPI in moderate or severe asthma. We also note that our analysis of GHG emission reductions achieved through improved diagnosis and disease management did not consider possible further reductions realised through averted exacerbations and hospitalisations49 as well as the carbon footprint of treating patients in intensive care units,100 which are all major contributors to healthcare emissions.
Finally, although this paper focuses on carbon footprint due to the urgent need to reduce GHG emissions by 2030,101 other environmental impacts of all inhaled devices may include water eutrophication and ecotoxicity but require further study.27 In the coming years, with advancement of: strategies to improve recycling and/or incineration of MDIs (allowing for recovery/disposal of unused propellant)27; propellant-free, reusable MDIs102; newer MDIs that use less propellant27; and MDIs that use new (lower global warming potential) propellants (eg, HFC-152a7 or HFC-1234ze103), the balance of environmental impacts between MDIs and DPIs may shift in the medium-term to long-term, stressing the importance of improving diagnosis and control to reduce overall inhaler use, rather than focusing primarily on switching from MDIs to DPIs.
Conclusions
Our analysis of the environmental impact of inhalers in asthma and COPD concludes that addressing misdiagnosis, reducing excess rescue inhaler use due to suboptimal baseline control and switching patients to lower global warming potential devices and/or regimens could result in GHG emission reductions of ~454 200 metrics tons per year in Canada. This would be the equivalent to taking ~101 100 gasoline-powered passenger vehicles off Canadian roads each year. As these gaps and patterns of care are common across countries, our findings should apply to other jurisdictions, though quantitative benefits will depend on local differences in the magnitude of care gaps and the existing balance between MDI and DPI use. Although previous literature has mostly focused on estimating the environmental impact of switching from MDI to DPI devices, our analysis shows that bridging fundamental care gaps with respect to misdiagnosis and optimal care could also have a dramatic carbon footprint impact. Accordingly, efforts to address GHG emissions from inhalers should focus on interventions to improve quality of care rather than solely on strategies to promote device substitution, given that the former will also improve patient outcomes. Although strategies to achieve the required changes in behaviour by both providers and patients are complex and multifold, the added incentive of these identified environmental benefits may provide a powerful additional motivator for change.