Dementia and personal identity: implications for decision-making

Changes in personality and judgment in dementia raise both practical and philosophic problems concerning personal identity. For example, if a patient's values and preference have been altered by disease, should caregivers' decisions for the patient be guided by their understanding of the patient's premorbid values and preferences, or of the patient's current values and preferences? Some authors have argued, based on philosophic accounts of personal identity, that the previously healthy person and the demented patient should be regarded as two different people; therefore, previous values and preferences lose their authority. Meanwhile, others have argued that when patients lose their ability to act autonomously, their "precedent autonomy" must be respected by following their earlier wishes. These debates can inform our thinking about the proper interpretation of advance directives, as well as other practical questions such as how carriers of dementia gene mutations should think about their future.