Demented subjects' competence to consent to participate in field studies: the Berlin Ageing Study.

A violation of the right to self-determination appears to be the main individual risk for participants in the Berlin Ageing Study, which is a community based non-therapeutic study with minimal health risk. In order to minimize the risk, a procedure to test the competence to consent to participate had to be introduced. To protect the participants' right to self-determination, basic capabilities of judgment and reasoning appear to be sufficient to give informed consent in this study. As a result of testing competency, 76% of the severely demented persons had to be excluded from the study, whereas a majority of the persons with mild to moderate dementia could be included.