Zhang Y, Pratap A, Folarin AA, Sun S, Cummins N, Matcham F, Vairavan S, Dineley J, Ranjan Y, Rashid Z, Conde P, Stewart C, White KM, Oetzmann C, Ivan A, Lamers F, Siddi S, Rambla CH, Simblett S, Nica R, Mohr DC, Myin-Germeys I, Wykes T, Maria Haro J, Penninx BWJH, Annas P, Narayan VA, Hotopf M, Dobson RJB. (2023). Long-term participant retention and engagement patterns in an app and wearable-based multinational remote digital depression study. NPJ Digital Medicine, 6(1), 25–25. https://doi.org/10.1038/s41746-023-00749-3

This paper reported findings related to long-term participant retention and engagement in a large observational digital study for depression, using survey and passive sensor data collected via smartphones and Fitbit devices. Participants (N=614) were recruited from three sites in the United Kingdom, Spain and Netherlands. Data were collected for up to 2 years by the EU research program RADAR-MDD. The majority of participants (68%) remained engaged in the study after 43 weeks. Smartphone and Fitbit usage data showed 3 distinct engagement subgroups for each data stream (most engaged, medium engaged, and least engaged). The least engaged group tended to have the highest depression severity and took significantly longer to respond to survey notifications. The least engaged were on average 5 years younger than the most engaged group. Roughly 45% of participants who stopped completing surveys after 8 weeks continued to share Fitbit data (average of 42 weeks). Findings could inform the design of future digital health studies to enable equitable and balanced data collection from diverse populations.