Return of Research Results to Participants in Longitudinal Cohort Studies in Health Research: Findings From 24 Cohorts of the Amsterdam Cohort Hub

ABSTRACT Background Returning research results to participants is increasingly recognised as part of participant‐centred health research. How this is implemented in longitudinal cohort studies is not yet well characterised. This study aims to provide a descriptive overview of current result return practices across diverse cohort studies in the Netherlands. Methods Drawing on the Amsterdam Cohort Hub, an infrastructure of population‐based and patient‐based cohorts in the Netherlands, representatives of 24 affiliated cohort studies completed a structured questionnaire administered via individual interviews. The questionnaire covered what results are returned, to whom, when and how. Individual‐level and group‐level return were distinguished. Cohorts also reported on motivations for returning results and barriers encountered in doing so. Data were summarised descriptively using frequencies. Results Individual‐level results beyond incidental findings were returned by 15 cohorts (65.2%), while group‐level results were returned by 23 cohorts (96%). Individual‐level return primarily involved physical and laboratory measures or was embedded in routine clinical care. Group‐level results were mainly shared through newsletters. Practices varied by cohort type and were shaped by ethical considerations and practical constraints. Concerns about participant misinterpretation and limited resources were the most reported barriers. Conclusion Return of research results is widely practised across cohort studies, but varies considerably in approach, shaped by ethical considerations, perceived communication risks, and financial and practical constraints. This descriptive overview of current practices may serve as a starting point for cohorts seeking to reflect on or develop their own result return procedures. Future research should examine the effects of various forms of result return on participant engagement and retention, as well as the role of participant preferences in shaping these practices. Patient or Public Contribution This study includes a descriptive inventory of patient and public involvement in longitudinal cohort studies, in the form of result return practices. The findings are directly relevant to research participants, as they concern how cohort studies communicate research results to the people who contribute their data. The results may inform how cohorts develop and improve their participant communication strategies in the future.