Understanding the effectiveness and underlying mechanisms of lifestyle modification interventions in adults with learning disabilities: a mixed-methods systematic review.

Background: Adults with learning disabilities face increased risks of unhealthy lifestyle behaviours, including alcohol consumption, smoking, low physical activity, sedentary behaviour and poor diet. Lifestyle modification interventions that target health-risk behaviours can prevent or reduce their negative effects. The goal of this project was to investigate the effectiveness and underlying mechanisms of lifestyle modification interventions in adults with learning disabilities. Methods: A systematic review and meta-analysis were conducted to determine the effectiveness of lifestyle modification interventions and their components in targeting health risk behaviours in adults with learning disabilities. Major electronic databases, clinical trial registries, grey literature, and citations of systematic reviews and included studies were searched in January 2021 (updated in February 2022). We included randomised and non-randomised controlled trials targeting alcohol consumption, smoking, low physical activity only, sedentary behaviour and poor diet in adults (aged ≥ 18 years) with learning disabilities. Studies were also coded based on the extent of use of theories and behaviour change techniques in interventions. Risk of bias in studies was assessed using appropriate tools. A realist synthesis of qualitative, quantitative and mixed-methods literature was conducted to complement the systematic review findings by identifying key intervention mechanisms that are likely to improve the health of adults with learning disabilities. Data were synthesised in the form of a programme theory regarding complex causal mechanisms and how these interact with social context to produce outcomes. All findings were integrated into a logic model. A patient and public involvement group provided input and insights throughout the project. Results: A total of 80 studies with 4805 participants were included in the systematic review. The complexity of lifestyle modification interventions was dismantled by identifying six core components that influenced outcomes. These components could be present in interventions targeting single or multiple health risk behaviors, either as individual elements or in various combinations. Interventions on alcohol and smoking behaviours were found to be effective, but this was based on limited evidence. The effectiveness of interventions targeting low physical activity only or multiple behaviours (low physical activity only, sedentary behaviours and poor diet) was mixed. All interventions had a varying level of statistical significance. The intervention-level network meta-analysis for weight management outcomes showed none of the interventions was associated with a statistically significant change in outcomes when compared to treatment as usual and each other. Similar findings were observed in the component network meta-analysis. A variety of theories and behaviour change techniques were employed in the development and adaptation of interventions. Most studies had a high and moderate risk of bias. A total of 79 studies, reporting the experiences of more than 3604 adults with intellectual disabilities and over 490 caregivers, were included in the realist synthesis. The resulting programme theory highlighted the contexts and mechanisms relating to support involvement, negotiating the balance between autonomy and behaviour change, fostering social connectedness and fun, the accessibility and suitability of intervention strategies and delivery, along with the broader behavioural pathways to lifestyle change. It also brought out the importance of working with people with lived experiences when developing and evaluating interventions. Our logic model, bringing together the findings of both syntheses, provides guidance on the design of future interventions. Discussion: This study was the first comprehensive mixed-methods evidence synthesis to explore lifestyle modification interventions targeting multiple unhealthy lifestyle behaviours in adults with learning disabilities. We conclude that future research could benefit from codeveloping interventions and population-specific assessment frameworks with people with lived experiences. There is a need for more high-quality research with appropriate outcomes and a focus on qualitative and mixed-methods research to better understand what works for whom and why. Trial registration: This trial is registered as PROSPERO CRD 42020223290. Funding: This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: NIHR128755) and is published in full in