Can Someone With Dementia Still Make Medical Decisions?

Many people have the mistaken impression that patients with dementia are incompetent to make medical decisions.

A person does not have to be “competent” to have medical decision-making “capacity”.  Competency is something only a judge can decide, whereas medical decision-making capacity can be determined by a physician.
A person with dementia may be incompetent to manage their financial affairs but still have the capacity to make informed decisions about whether to have surgery or decline CPR.

In general, to make any informed consent, four elements of information must be provided:  the nature of the ‘procedure’; the benefits; the risks (both common and severe); and if there are any alternatives.  In addition, it must be voluntary; and the patient must have the capacity to understand what’s to be done.
Someone with dementia is only “incapacitated” to make a decision if they cannot:  understand the nature of the procedure, evaluate the information, appreciate the consequences, make a decision that’s consistent over time, or communicate their decision.

Essential to this process is providing the information in a form understandable to the patient and allowing them time to think about it.  Although doctors usually make a recommendation, studies show that patients and their families still want adequate information so that they can make a shared decision with the physician.   
Thus, only patients with late-stage dementia are truly incapable of making most medical decisions.  And when that stage is reached, if they have an Advance Directive in place, it will help avoid care they would not have wanted and guide their Healthcare Proxy (or Durable Power of Attorney) in making decisions that are in the best interests of that patient.