BackgroundThe UN Convention on the Rights of Persons with Disabilities, and the reformed guardianship law in Germany, require that persons with a disability, including people with dementia in Alzheimer’s disease (PwAD), are supported in making self-determined decisions. This support is achieved through communication. While content-related communication is a deficit of PwAD, relational aspects of communication are a resource. Research in supported decision-making (SDM) has investigated the effectiveness of different content-related support strategies for PwAD but has only succeeded in improving understanding, (...) which, although one criterion of capacity to consent, is not sufficient to ensure overall capacity to consent. The aim of the ‘spatial intervention study’ of the DECIDE project is to examine an innovative resource-oriented SDM approach that focuses on relational aspects. We hypothesise that talking to PwAD in their familiar home setting (as opposed to a clinical setting) will reduce the complexity of the decision-making process and enhance overall capacity to consent. MethodsPeople with a suspected or confirmed diagnosis of dementia in Alzheimer’s disease will be recruited from two memory clinics (N = 80). We will use a randomised crossover design to investigate the intervention effect of the decision-making place on capacity to consent. Besides reasoning capacity, which is part of overall capacity to consent and will be the primary outcome, various secondary outcomes (e.g., other aspects of capacity to consent, subjective task complexity, decisional conflict) and suspected moderating or mediating variables (e.g., meaning of home, demographic characteristics) will be assessed.DiscussionThe results of the study will be used to develop a new SDM strategy that is based on relational resources for PwAD. If a change in location achieves the anticipated improvement in capacity to consent, future research should focus on implementing this SDM strategy in a cost-effective manner in clinical practice.Trial registration: DRKS00030799. (shrink)