The capacity to vote in patients with mental illness is increasingly questioned. The objective of this study is to evaluate this capacity in a group of subjects with dementia (Alzheimer's disease) and other elderly subjects without dementia. With a sample of 68 subjects with dementia and 25 controls living in a senior residence, a transversal study was carried out over 4？months. Subjects were evaluated with the Mini-Mental State Examination (MMSE) and the Competence Assessment Tool for voting (CAT-V). The results were more positive for the Doe criteria (as part of the CAT-V), and a correlation was found with the MMSE in subjects with dementia and, to a lesser degree, in the controls. We conclude that the capacity to vote is related to cognitive deterioration and, within that, is more related to understanding and appreciation. 1. Introduction Voting is a legal right in many countries. But the exercise of this right does not mean that all persons have the capacity to vote. There might be cases of people with the competence to vote, but without the necessary capacity. For this reason, there is increasingly more literature seeking a tool to evaluate the capacity to vote, for patients with dementia as well as other mental disorders, such as those hospitalized with acute symptoms, and so forth [1–4]. In the evaluation of the capacity for the act of voting, there are 6 questions that evaluate the functional abilities of the person, based on the 4 standard decision-making abilities: understanding, choice, reasoning, and appreciation. Some of these questions come from the standard questionnaire of a federal court, related to understanding the nature of voting, understanding its effect and vote selection in Maine, USA (Doe criteria) . In addition, items have been added incorporated in the CAT-V test : comparative reasoning, consequential reasoning, and appreciation. This instrument has been used in various studies [2–4]. However, doubt persists as to which items to use for screening and to which persons. What should be the cutoff point? Should some items be weighted more than others? Our study attempts to resolve these questions in two ways: using the MMSE  as a cognitive variable and the CAT-V as a voting test in two samples: one group of patients with Alzheimer’s dementia living in a senior residence and a second group of persons living in the same residence who suffer no mental illness. 2. Materials and Methods 2.1. Participants The study included 68 patients residing in the Arganda del Rey Senior Residence, diagnosed with Alzheimer’s dementia
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