External validity of epidemiological studies largely depends on the representativeness of the actual study sample, in turn the internal validity is reduced if selection is biased. Community participation in all the phases of an epidemiological study is a crucial element of this representativeness, and to keep potential selection bias at bay. This project aims to investigate the motivations in favor and against participation in research among older adults. We use qualitative methods to elicit themes relevant to inform the design and conduction of SwissDEM, an epidemiological study on aging and dementia. We conducted in depth interviews, semi-structured with twenty-two older adults (65+) who took part in the validation phase of SwissDEM. The thematic analysis of the interviews, which were audio and video recorded, allowed developing an ad hoc communication strategy for the recruitment of participants. In particular, through the involvement of the population in the co-construction of a communication campaign, we aim to increase participation to SwissDEM.