Determinants of Capacity to Consent to Research on Alzheimer's disease

Investigators conducting Alzheimer's disease (AD) research need to consider participants' capacity to consent. Cognitive functioning is a significant predictor of decisional capacity, but there is a dearth of information on the influence of neuropsychiatric symptoms in AD on decisional capacity. We examined the rates of decisional capacity associated with two types of research protocols, and the association of capacity with neuropsychiatric symptoms and other participant characteristics.

We comprehensively evaluated decisional capacity among 64 patients with mild-to-moderate AD and 70 healthy comparison (HC) subjects randomized to consider either a medium risk or higher risk hypothetical research protocol. Additional measures included sociodemographics, cognitive deficits, and neuropsychiatric symptoms.

Twenty AD patients (31.3%) and 67 HCs (95.7%) were deemed capable; 44 AD patients (68.8%) and 3 HCs (4.3%) incapable of consent. Age, education, and severity of cognitive deficits were associated with incapable status; there were no significant associations with severity of neuropsychiatric symptoms or protocol risk level.

Findings highlight the importance of understanding of capacity and its assessment among people with AD, rather than treating AD diagnosis as synonymous with impaired capacity. As novel treatments move from bench to bedside, methods of assessing and addressing capacity impairment must similarly advance.

In assessing research consent capacity, use structured assessments with population specific cut scores interpreted in the context of the person's background including education, culture, and language. Individuals should be encouraged to execute research proxy documents when able.