Someone who needs a hospital is telling you no. What their dementia does and doesn't change about that, and how to make the refusal unnecessary.
Notice the assumption forming. The diagnosis is on the medication list, they're confused, they're refusing, and the conclusion writes itself: they can't decide this, so the decision isn't theirs. That conclusion is wrong often enough to be worth one deliberate pause. Dementia and incapacity are not the same finding, and treating them as the same is its own liability.
Start with the clinical point that governs everything else. A cognitive disorder does not by itself impair decision-making capacity. Dementia is a reason to assess capacity carefully and document it, not a reason to assume it's absent. Capacity is also decision-specific and can fluctuate: a person may lack the capacity to manage their finances and still have the capacity to refuse a ride to the hospital, and someone assessed at noon may be different at ten at night.
Keep capacity and competence separate. Competence is a legal status determined by a judge, and someone with a court-appointed guardian has already been found unable to represent themselves. Capacity is your clinical assessment, right now, in this living room. You will almost never have a judicial determination in front of you, so the assessment and the documentation of it are the whole job.
Hypoxia, hypoglycemia, shock or hypotension, infection and sepsis, head injury, stroke, and medication effects can all produce or deepen an impaired mental state, and several of them are the actual emergency you were called for. An impaired mental state that arrived tonight is a different finding from baseline dementia, and it is the one that most often changes the disposition.
Communication guidance only. Follow applicable law, your EMS system's protocols, and medical-control direction.
Refusal policy, capacity documentation language, medical control thresholds, and the role of law enforcement in a transport under implied consent are all set by your agency and your region, and they vary. Nothing here replaces them. This page is about reading the person in front of you accurately enough that the protocol question comes up less often.
Most of these refusals aren't a decision being made. They're a person who can't hold onto why strangers are in their house, doing the only thing still available to them.