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 (