Abstract
Background: Adults with learning disabilities have an increased disposition to unhealthy lifestyle behaviours which
often occur simultaneously. Existing studies focus on complex interventions targeting unhealthy diet, physical
inactivity, sedentary behaviour, smoking, and alcohol use to reduce health risks experienced. It is essential to
understand how well these interventions work, what works, for whom, in what context and why. This study aims to
investigate the effectiveness and underlying mechanisms of lifestyle modification interventions for adults with
learning disabilities.
Methods: This is a mixed-methods systematic review consisting of a network meta-analysis (NMA) and realist
synthesis. Electronic databases (ASSIA, CINAHL, EMBASE, MEDLINE, and PsycINFO) will be searched from inception to
14 January 2021 with no language restriction. Additionally, trial registries, grey literature databases and references
lists will be searched. Studies related to lifestyle modification interventions on the adult population (>18 years) with
learning disabilities will be eligible for inclusion. Two independent researchers will screen studies, extract data and
assess its quality and risk of bias using the Cochrane Collaboration’s Risk of Bias Assessment Tool (RoB Version 2)
and ROBINS-I. The strength of the body of evidence will be assessed based on the GRADE approach. The NMA will
incorporate results from RCTs and quasi-experimental studies to estimate the effectiveness of various lifestyle
interventions. Where appropriate, a component NMA (CNMA) will be used to estimate effectiveness. The realist
synthesis will complement and explain the findings of NMA and CNMA by including additional qualitative and
mixed-methods studies. Studies will be included based on their relevance to the programme theory and the rigour
of their methods, as determined by quality appraisal tools appropriate to the study design. Results from both
syntheses will be incorporated into a logic model.