Remote Longitudinal Tracking of Sleep, Depression, and Cognition Across Early Adolescence: Protocol for a Longitudinal Observational Study.

Background: Depression in adolescents is a growing public health concern, with 3.5 million youth in the United States experiencing a depressive episode each year. When symptoms emerge in early adolescence, they can have lasting psychological, physical, and cognitive consequences, highlighting the urgent need for proactive intervention. Insufficient sleep-characterized by short duration, irregular timing, and poor quality-is bidirectionally linked to depression and associated with impaired cognitive performance. Objective: This protocol provides the map for a study tracking sleep patterns and neurophysiology, as well as a range of depressive symptoms, and their dynamic interaction in shaping longitudinal cognitive trajectories. Methods: Fifty-six youth aged 9 to 13 (mean 11.01, SD 1.39) years were enrolled in a longitudinal measurement burst design comprising 4 assessment waves at baseline, 4, 8, and 12 months. We recruited a sample of youth with a range of depressive symptom severity. Each wave included 7 consecutive days of monitoring during which participants used a personalized mobile health (mHealth) platform, HowRU app, developed by the study team, to report daily sleep patterns, thrice-daily ecological momentary assessments (EMAs), and completed a series of cognitive tasks. Youth and parents also completed validated psychosocial questionnaires to assess mood, behavioral concerns, mental health, and sleep. Sleep and physical activity were monitored remotely using a Garmin VivoSmart 5 watch and Interaxon Muse S headbands. Sleep-dependent cognitive performance was assessed with 2 declarative memory tasks (Word-Pair Associates task [WPA] and Minecraft Memory and Navigation [MMN] task), a procedural memory task (Motor Sequence task), and 2 executive functioning tasks (Operation Span [OSpan] task and Rule Switch task [RST]). For the memory tasks, participants completed training and immediate testing in the evening, followed by a retention test the following morning. The OSpan task and Rule Switch were administered twice daily (morning and evening). For all tasks, stimuli were randomized and counterbalanced across participants and testing sessions. Results: Funding was obtained from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (grant K08 HD107161), with a budget period of August 1, 2022, to July 31, 2027. Participant enrollment occurred May 2023 through October 2024. Data collection began in July 2023 and was completed in October 2025. Study participant retention and adherence rates for sleep diaries, cognitive tasks, and questionnaires were high. Primary outcomes of the study are anticipated to be published in fall 2026. Conclusions: This protocol provides a robust and reproducible framework to longitudinally track youth with a range of depressive symptoms in the real world using mHealth platforms and wearable technology. Potential findings can support the identification of key developmental periods of vulnerability and resilience in youth, inform future sleep-based interventions to promote mental health, and optimize cognitive outcomes across early adolescence.