Executive dysfunction and loss of capacity to consent to medical treatment in patients with Alzheimer's disease.

Loss of medical decision making capacity (competency) is an inevitable consequence of Alzheimer's disease (AD) and is an important subject for neuropsychological investigation. Consent capacity involves a complex set of comprehension, encoding, information processing, decision making, and communication abilities, which ultimately must have an explicit neurological basis. This article examines the role of executive dysfunction in loss of consent capacity in patients with AD. The authors first describe a cognitive neuropsychological model for understanding loss of consent capacity in AD. The article also reviews neuropsychological studies that have used a psychometric instrument to test consent capacity under different legal standards (Capacity to Consent to Treatment Instrument). These studies indicate that when multiple cognitive functions are associated with declining competency of AD patients on the Capacity to Consent to Treatment Instrument legal standards, measures of simple executive function are the predominant predictors. These empirical findings are discussed and related to the conceptual model. The findings support the growing body of literature linking frontal neural systems and executive cognitive functions to competency and to higher order functional capacities.