Neuropsychological predictors of decision-making capacity over 9 months in mild-to-moderate dementia.

BACKGROUND: Older adults with dementia may have diminished capacity to make medical treatment decisions.
OBJECTIVE: To examine rates and neuropsychological predictors of treatment decision making, or consent capacity, among older adults with dementia over 9 months.
DESIGN: Consent capacity was assessed initially and 9 months later in subjects with and without dementia using a longitudinal repeated measures design. PARTICIPANTS: Fifty-three older adults with dementia and 53 similarly aged adults without dementia. MEASUREMENTS: A standardized measure MacArthur Competence Assessment Tool-Treatment of 4 legal standards for capacity (Understanding, Appreciation, Reasoning, and Expressing a Choice) and a neuropsychological battery.
RESULTS: In the dementia group, 9.4% had impaired capacity initially, and 26.4% had impaired capacity at 9 months. Mean scores in the dementia group were impaired relative to controls initially and at 9 months for Understanding (initial t=2.49, P=.01; 9-month t=3.22, P<.01) and Reasoning (initial t=2.18, P=.03; 9-month t=4.77, P<.01). Declining capacity over 9 months was attributable to a further reduction in Reasoning (group x time F=9.44, P=.003). Discriminant function analysis revealed that initial scores on naming, delayed Logical Memory, and Trails B were associated with impaired capacity at 9 months.
CONCLUSIONS: Some patients with mild-to-moderate dementia develop a clinically relevant impairment of consent capacity within a year. Consent capacity in adults with mild-to-moderate dementia should be reassessed periodically to ensure that it is adequate for each specific informed consent situation. Interventions that maximize Understanding and Reasoning by supporting naming, memory, and flexibility may help to optimize capacity in this patient group.