Patterns of rest-activity rhythms from adolescence to young adulthood: a scoping review

Introduction: Rest-activity rhythms (RAR) measure daily physical activity patterns. RAR metrics correlate with biopsychosocial trajectories in adults and may represent objective biomarkers of health and risk. However, the significance of RAR to demographical, physical, and psychological factors in early adolescence and young adulthood has not been collectively evaluated, leaving gaps in understanding RAR's relevance during this developmental window. Methods: A systematic search identified peer-reviewed studies on adolescents and young adults (ages 10-19) that reported data on RAR variables and factors of interest published through April 2024. Study and participant characteristics, device characteristics, days of wearable data collected, RAR variables, and associated demographic, social, physical, and psychological factors were extracted. Results: Of 1,648 screened titles and abstracts, 19 studies with 16,717 participants met eligibility. Included studies varied widely in devices used, epoch lengths, recording duration, and RAR data compliance criteria. Seven studies reported RAR outcomes relevant to demographic or social factors, nine studies reported RAR outcomes relevant to physical health, and ten studies reported RAR results relevant to psychological factors. Across domains, findings were highly heterogeneous and differed from the more consistent and established associations observed in the adult literature. Generally, age-related decreases in stability and fragmentation were observed, as well as associations between increased fragmentation and cardiometabolic risk and between reduced peak daytime activity and poor mental health. Consistently, younger age groups exhibited higher interdaily stability and intradaily variability, and elevated cardiometabolic risk was associated with a delayed acrophase. Methodological inconsistencies and low-quality studies limit the generalizability of findings across studies. Conclusion: Standardization in RAR measurement, establishment of age- and sex-specific normative values for RAR, and longitudinal studies with more diverse samples are necessary to advance this field and better clarify clinically relevant RAR associations.