A peer-group programme for people with severe mental illness to reduce risk of cardiometabolic disease (PEGASUS): protocol for a feasibility study

Background People diagnosed with severe mental illness (SMI) die around 15–20 years prematurely compared with people without these conditions, partially to a 50% increased risk of developing Cardiovascular disease (CVD). Treatment and diagnosis rates of CVD and metabolic disease (together called Cardiometabolic disease) are lower in people diagnosed with SMI, at a considerable cost to individuals and their families, health services, and society. Previous trials have shown that Behaviour change interventions to reduce cardiometabolic risk, when delivered alone, produce modest results at best. PEGASUS aims to co-design a peer-led group intervention with lived experience and which includes social integration and peer support along with behaviour change to reduce cardiometabolic risk in people diagnosed with SMI. Methods This is a multi-site single arm mixed methods study based in three National Health Service (NHS) Mental Health Trusts in England, aiming to test the feasibility of the PEGASUS intervention and its future evaluation in a large-scale randomised controlled trial. Over six months, participants aged 18–75, with a diagnosis of SMI and enhanced Cardiovascular disease risk will attend ten fortnightly support groups led by a peer support worker and a health care professional, focusing on physical health, both general and specific to those diagnosed with SMI. Additionally, there are four one-to-one sessions with a peer support worker and a booster session three months after the intervention has ended. Biometric, accelerometer, behavioural and psychometric questionnaire data will be collected at baseline, three months, and six months, accompanied by qualitative interview and focus group data at three and six months. The feasibility and acceptability of each measure will also be measured. Quantitative data will be analysed using STATA and qualitative data will be analysed with NVivo using rapid framework analysis. Discussion This study will determine the feasibility and acceptability of a peer-led group programme to reduce Cardiovascular disease risk in people diagnosed with SMI. The results will inform the PEGASUS randomised controlled trial. Trial registration This study was approved by the Health Research Authority and Wales Research Ethics Committee (IRAS: 326517) on 3rd September 2024 and was registered with the ISRCTN (29596999) on 18th August 2025.