Older adults' motivations to participate or not in epidemiological research. Qualitative inquiry on a study into dementia in Switzerland.

Our thematic analysis revealed that older adults hold specular motivations in favour and against participation to research. Studying jointly motivations in favour and against provides information for recruitment strategies and to overcome barriers to participation, respectively. Participatory action research can inform the design and conduction of and should precede epidemiological studies in older adults, and can potentially contribute to attain high response rates.