Strategies for engaging "hard-to-reach" populations in a panel for digital health research: A qualitative study among experts.

Digital health technologies are developed to aid individuals in managing their health. Nonetheless, a significant number of these technologies remain neither implemented nor utilized by potential end users. One contributing factor to this gap in uptake is the insufficient consideration of the target audience needs and requirements during the development phase of these technologies. Moreover, certain groups in society are often underrepresented in such research projects (so called "hard-to-reach"), leading to a disconnect between the developed technologies and their needs and requirements. However, recruiting a representative study population - including individuals from different demographic backgrounds - for such studies poses challenges for researchers. One proposed solution is panel research, wherein a fixed group of participants is willing to participate in multiple research projects over time. In this study, we conducted semi-structured interviews with twelve experts in panel management or with researchers working with individuals in a vulnerable position, to gain insights into their experiences. Through thematic analysis, four key themes emerged: diverse recruitment strategies, investment in sustainable participation, simplified informed consent, and regulating practical matters. Recruiting a representative study population requires diverse and active strategies, such as visiting community centres and leveraging key figures. Long-term engagement can be maintained through regular, accessible communication, flexible participation options, and aligning research goals with participants' interests. Additionally, clear expectations, a supportive environment, respect for privacy, and feedback and incentives are crucial for retaining panel members. Taken into account these factors support inclusiveness in digital health research. Ultimately resulting in better alignment between users' needs and the development, implementation and adoption of digital health technologies.