Effectiveness of Interventions to Reduce Carbon‐Emissions Within Secondary Healthcare: Systematic Review and Evidence and Gap Map

‘The climate emergency is also a health emergency’ (England 2024). Climate change directly impacts the health of the human population through events such as earthquakes, flooding, heatwaves and drought, which increase the risk of injury, displacement, disruption of food supplies, infectious diseases and mental ill health (England 2024; Lenzen et al. 2020; Tennison et al. 2021; The Lancet Respiratory Medicine 2023). The impact on population health of these climate events, alongside indirect health consequences such as increased prevalence of respiratory conditions due to air pollution, places an increased burden on health services (Royal College of Physicians 2017). The environmental footprint of healthcare services contributes between 1% and 5% towards total global environmental impacts (Lenzen et al. 2020; Tennison et al. 2021). Reducing the impact of the healthcare system on climate change has the potential to benefit population health through improved air quality and diet, and increased activity levels (Mailloux et al. 2021). Due to the lack of systematic reviews which consider carbon emissions associated with the patient pathway within individual specialities, further research is needed to enable the identification and transformation of the most carbon‐intensive clinical pathways, while ensuring future models of care can be delivered in a cost‐effective manner without increasing emissions or compromising patient care. In 2008, the Climate Change Act set national targets for the 100% reduction of carbon emissions in England to 1990 levels by 2050 (‘Climate Change Act’ 2008). Within the United Kingdom, the National Health Service (NHS) has an important role in helping to achieve these targets, as the organisation accounts for 4% of England's carbon footprint (NHS England 2022). The UK government's Greener NHS team from NHS England asked the Exeter Policy Research Programme Evidence Review Facility to bring together and analyse research which assesses different ways carbon emissions resulting from hospital‐led care can be reduced, without affecting the care patients receive in hospitals, at home and in clinics. Work focusing on identifying and delivering interventions to reduce carbon emissions within known carbon hotspots, such as NHS estates and facilities, travel and transport, supply chain, and certain medicines and medical and anaesthetic gases that have high global warming potential is already underway, alongside examining the effectiveness of different models of care delivery across all specialities (NHS England 2022; NHS Shared Business Services 2022). Evidence focusing on the effectiveness of interventions in reducing carbon emissions within secondary healthcare would be a useful complement to this work. An approach which considers the patient pathway may be beneficial in identifying interventions which consider wider healthcare systems and thus have a meaningful impact on reducing carbon emissions. This review was commissioned by the Greener NHS team and could serve as a useful case study for wider net‐zero ambitions elsewhere in the world. We aimed to carry out a systematic review examining the effectiveness of interventions in reducing the carbon footprint within specific medical specialities in secondary healthcare and explored where this evidence could inform the patient care pathway. In July 2023, we searched a selection of bibliographic databases with coverage of both health care and environmental science journals, including MEDLINE, Embase and Environment Complete, which we supplemented by inspecting the HealthcareLCA database, conducting forwards and backwards citation chasing on all studies which met our inclusion criteria, searching reference lists of topically relevant reviews, and searching Google Scholar and a selection of relevant websites. We included studies using any comparative study design evaluating any intervention intended to reduce the environmental impact of a procedure, process, treatment, or pathway delivered within secondary healthcare in the following specialities: cardiology, gastroenterology, obstetrics, oncology, ophthalmology, orthopaedics and trauma, radiology, renal, respiratory and high volume, low complexity surgeries (specifically: ear, nose, and throat [ENT], gynaecology and urology). We extracted descriptive data regarding study sample, intervention/control group, carbon emission methodology, PROGRESS‐PLUS criteria (related to equity) and environmental, patient and cost outcomes. We appraised the quality of studies using life cycle assessment (LCA) methods with a predetermined scoring system informed by Weidema's (1997) guidelines (B.P.W. 1997). We synthesised findings from studies drawing on LCA methods and non‐LCA studies separately using narrative synthesis. Within each group, studies were clustered into five broad intervention categories: (1) Accessing care, (2) Product level, (3) Care delivery, (4) Setting and (5) Multiple components. We examined and explained patterns across studies within the same speciality which evaluated similar interventions. We also developed an evidence and gap map (EGM) to highlight where evidence relevant to the review aims could inform a generic patient care pathway for each speciality and future research on lower carbon pathways. Input from the Greener NHS team at NHS England, LCA methods experts and patient and public representatives was incorporated throughout. Eighty‐eight studies (92 articles) met eligibility criteria, 28 used LCA‐informed methods to calculate carbon emissions (19 of these utilised a full LCA approach). Of the LCA studies, 9 were of Low risk of bias, 14 of Medium risk of bias and 5 of High risk of bias. Urology (n = 14), gastroenterology (n = 13), oncology/radiation oncology (n = 13) and renal (n = 11) were the most common specialities represented. Across different specialities, most evidence was found in the first three stages of the patient care pathway (Initial assessment/diagnostic tests, initial treatment, or routine follow‐up). The exception was the renal speciality, where most evidence was within ‘Ongoing care’ segment. There was limited evidence within the ‘Discharge’ segment of the care pathway across all specialities. Evidence relating to the wider healthcare setting was clustered within gastroenterology (n = 5) and radiology specialities (n = 5). The two largest groups of evidence were for studies evaluating telehealth (n = 26) and reuseable equipment (n = 13) interventions. Telehealth interventions were predominantly evaluated using non‐LCA methods (n = 23). While carbon‐emissions favoured telemedicine interventions versus face‐to‐face care, these calculations often only considered patient‐travel saved and did not account for carbon emissions associated with other parts of the delivery of the service, such as digital technology used or energy use of building or clinic equipment for face‐to‐face appointments, or wider impact on the patient care pathway such as potential need to travel for additional primary care appointments. The majority of patient and cost outcomes favoured telemedicine interventions, although most were based on non‐statistical analyses. Interventions comparing carbon emissions associated with the use of reuseable versus disposable surgical equipment represented the largest group of studies using LCA methods. For studies within gastroenterology, reuseable equipment was associated with reduced carbon emissions. Within urology, this finding was reversed, although questions regarding the accuracy of use of characterisation factors, quantity of materials used in disposable versus reuseable equipment packs and how carbon emissions were assigned to the reprocessing of reuseable equipment mean confidence in this finding is uncertain. While waste management/reduction interventions were associated with reduced carbon emissions, interventions were highly heterogeneous, with limited consideration of patient or cost outcomes. Eight non‐LCA studies found that reduced carbon emissions were associated with energy conservation interventions, such as turning equipment off when not in use or choosing imaging techniques with lower energy use, the majority of which were conducted within radiology/radiotherapy settings. This systematic review synthesises quantitative evidence evaluating the effectiveness of interventions intended to reduce carbon emissions within high‐volume secondary healthcare specialities. It highlights a highly heterogeneous evidence base, and the methodological limitations associated with studies based on LCA and non‐LCA methods. While we identified several large clusters of studies evaluating similar interventions within the same speciality, future research needs to address these methodological limitations to support confident decision‐making within policy commissioning and clinical practice. Our EGM displays the included evidence according to individual speciality along the patient pathway, enabling evidence users to identify research which meets their requirements as well as identifying potential gaps where further research may be required.