Determining a patient's decision-making capacity is a core aspect of medical practice to uphold the ethical principle of autonomy. This becomes especially salient in dementia care, with complex decisions regarding therapeutics and care planning are critically important in balancing autonomy with safety. Although decision-making capacity often deteriorates in individuals with dementia, the exact point at which this happens across dementia subtypes is incompletely understood. In this study, we explored the relationship between dementia staging and decision-making capacity across dementia subtypes.

At a tertiary care memory center, 185 patients with mild cognitive impairment (MCI) or dementia were enrolled at point of care during their medical appointment. Demographic and diagnostic data were collected. Patients were administered the Montreal Cognitive Assessment (MoCA) and Capacity to Consent to Treatment (CCTI). A logistical regression was used to model the probability of retained decision making capacity as a function of disease stage and diagnosis. 

Using a descriptive pattern in predicted probability of decision-making capacity, individuals with frontotemporal dementia (FTD) appeared to lose capacity slightly earlier compared to the cohort of all MCI and dementia subtypes. However, this finding did not reach statistical significance. Using a similar model, Alzheimer’s disease (AD) did not differ substantially from the group.

Our findings suggest that individuals with FTD may lose decision making capacity earlier in their disease course than other dementia subtypes, including AD. This suggests that frontal lobe functions such as judgment and reasoning that are affected early in FTD, rather than memory decline or anosagnosia as seen in AD, predict decision-making capacity in individuals with MCI and dementia. Future higher-powered studies are needed to further investigate this finding.