Supporting continuous glucose monitoring for people with serious mental illness and type 2 diabetes: a co-design study for a structured intervention.

Introduction: Individuals with serious mental illness (SMI), such as schizophrenia or bipolar disorder, are at a two- to threefold increased risk of developing type 2 diabetes and face significant health inequalities, including reduced life expectancy. Diabetes self-management in this population is challenging, and existing interventions are poorly suited to their needs. Continuous glucose monitoring (CGM) offers potential benefits but remains underused. This study aimed to co-design a logic model and programme theory for a structured CGM intervention tailored to adults with SMI and type 2 diabetes, as a resource to support the planned future co-production of the content and the implementation of the full intervention. Methods: Using experience-based co-design, this study engaged service users, carers, and healthcare professionals (HCPs) in workshops and discussions to identify challenges and facilitators for CGM use. Participants co-developed an outline of candidate intervention components, which were summarised in a logic model and programme theory. The process included synthesising existing evidence, exploring personas, and mapping CGM user journeys. The draft intervention outline was iteratively refined across multiple sessions. Results: Ten participants (four HCPs, four service users, and two carers) contributed to the co-design process. Barriers identified included limited technical support, accessibility challenges, and a lack of integrated physical and mental healthcare. Key components for a structured CGM intervention include personalised CGM training, flexible delivery methods, ongoing support, and peer networks. The proposed intervention was conceptualised in three phases: set-up, early days, and living with CGM. Participants prioritised flexibility and tailored intervention adjustments, emphasising the importance of addressing both physical and mental health needs concurrently. Discussion: This study demonstrates the feasibility of co-designing interventions with individuals often considered "hard to reach." Our study highlights that people with SMI can take an interest in their physical health and see the potential for CGM to improve diabetes management, provided they receive appropriate and flexible support. Future work will develop and refine the intervention and evaluate its clinical and cost-effectiveness in diverse populations, aiming to address significant unmet needs in diabetes care for this vulnerable group. Study registration: https://osf.io/4ae3g/ (2 February 2024).