We will seek care home managers' agreement for their care home's inclusion. We will note refusal, in order to consider external validity and use its predictors in a sensitivity analysis. In included homes, we will identify through the home care staff which people cared for have dementia using a carer proxy measure, the Noticeable Problems Checklist (Levin 1989) if they do not have a known dementia diagnosis. We will do this rather than screening residents using a cognitive measure, as it will not cause distress and is independent of culture and education. We will invite all people with dementia to participate.