Developing and Evaluating Behaviour Change Interventions for People with Younger-Onset Type 2 Diabetes: Lessons and Recommendations from Existing Programmes.

People with younger-onset type 2 diabetes (YOT2D, diagnosis before 40 years of age) are at higher risk of morbidity and premature mortality compared with their similar-age type 1 diabetes and later-onset type 2 diabetes peers. Despite recommendations for targeted, behavioural, and psychosocial approaches to optimising health outcomes, there are few such interventions for this group. Furthermore, evaluations of health behaviour change interventions targeting this priority population have proven challenging to complete. Despite this, there is little guidance for future behavioural programme developers. The aims of this paper are to synthesise lessons learned and recommendations from published evaluations of YOT2D-focused health behaviour change interventions, and illustrate challenges and solutions using case studies from our own experience. A rapid review of the literature identified 11 trials of behavioural interventions for YOT2D (5 randomised controlled trials, 6 pre/post studies). We sourced related needs assessment and development papers to describe the life course of each programme. We identified two development and two evaluation-related themes impacting successful trial execution. Development recommendations include ensuring appropriate adaptation of existing interventions to the unique challenges and characteristics of the target group, use of theory or theoretical frameworks throughout, and involvement of the priority population and key stakeholders from inception. Evaluation recommendations include planning for meaningful evaluation and development of age-appropriate Core Outcomes Sets. Future programme developers would benefit from closer attention to intervention development guidelines and a focus on supporting those with YOT2D to achieve behaviour change and diabetes self-management goals, ahead of change to biomedical outcomes.