Embedding a user-centred approach in the development of complex behaviour change intervention to improve outcomes for young adults living with type 1 diabetes: The D1 Now Study.

Type 1 diabetes (T1D) is an auto-immune condition which requires intensive self-management. Diabetes self-management is challenging, especially during young adulthood. Effective interventions to improve outcomes for young adults with T1D are needed. This paper describes the development of the D1 Now intervention, employing a user-centred approach to engage with stakeholders in parallel with the application of theory. Intervention development consisted of 4 phases: 1) the formation of a public and patient involvement (PPI) Young Adult Panel (YAP); 2) a systematic review to synthesise evidence regarding the effectiveness of interventions aimed at improving outcomes for young adults with T1D; 3) understand young adults' diabetes self-management behaviour through engagement with key stakeholders; and 4) an expert consensus meeting to discuss self-management strategies identified in Phase 1 and 3 that would form the core components of the D1 Now intervention. The YAP resulted in meaningful involvement between young adults, researchers and service providers. The systematic review highlighted a lack of quality intervention studies. Qualitative findings highlighted how young adult self-management is driven by complex interactions between external resources, which influence capability, and motivation. The expert panel in Phase 4 highlighted focus areas to improve outcomes for young adults and implementation strategies. Subsequent to these 4 phases, 3 intervention components have been identified: 1) a key worker to liaise with the young adult; 2) an online portal to facilitate relationship building between staff and young adults; and 3) an agenda setting tool to facilitate joint decision-making. This study described the systematic development of an intervention underpinned by theoretical frameworks and PPI, and has identified components for the D1 Now intervention. The resulting intervention content will now be subject to an intervention optimisation process.