Retention of Ethnic Participants in Longitudinal Studies.

We aimed to identify effective participant retention strategies utilized in longitudinal studies of ethnic groups, specifically those from South Asian and Chinese communities. We conducted a systematic review of the literature focusing on the retention of ethnic minorities in longitudinal studies, up until April 2017. Only peer-reviewed research was included. 11,316 citations were retrieved, of which 4808 were duplicates and 51 met the inclusion criteria. Financial incentives, involving key community members, flexible scheduling, developing trust and personal connections with participants, and having extensive participant contact information are key facilitators. We also describe our extensive experience of retaining South Asian and Chinese participants in longitudinal studies. Key retention strategies for these groups include involving family members, informing participants about potential personal and community benefits, being flexible in how and when the interviews are conducted, and providing multiple language options. There is little published evidence or direction regarding how to retain study participants from South Asian or Chinese communities. However, there can be some learning from studies focused on other ethnic groups. Establishing an evidence-based approach, including facilitators and barriers to retention of these groups in longitudinal studies would help to determine study feasibility, validity, and ultimately to reduce health disparities among South Asian or Chinese communities.