Cohort profile: TheSmartSleep Study, Denmark Triangulation of evidence from survey, clinical and tracking data
Authors: Rod NH , Andersen TO , Severinsen ER , Sejling C , Dissing AS , Pham VT , Nygaard M , Schmidt LKH , Drews HJ , Varga TV , Freiesleben NlC , Nielsen HS , Jensen AK 
Published: December 2022

ABSTRACTPurposeTheSmartSleep Studyis established to comprehensively assess the impact of night-time smartphone use on sleep patterns and health. An innovative combination of large-scale repeated survey information, high-resolution sensor-driven smartphone data, in-depth clinical examination and registry linkage allow for detailed investigations into multisystem physiological dysregulation and long-term health consequences associated with night-time smartphone use and sleep impairment.ParticipantsTheSmartSleep Studyconsists of three interconnected data samples, which combined include 30,673 individuals with information on smartphone use, sleep and health. Subsamples of the study population also include high-resolution tracking data (n=5,927) collected via a customized app and deep clinical phenotypic data (n=245). A total of 7,208 participants will be followed in nationwide health registries with full data coverage and long-term follow-up.Findings to dateWe highlight previous findings on the relation between smartphone use and sleep in theSmartSleep Study, and we evaluate the interventional potential of the citizen science approach used in one of the data samples. We also present new results from an analysis in which we utilize 803,000 data-points from the high-resolution tracking data to identify clusters of temporal trajectories of night-time smartphone use that characterize distinct use patterns. Based on these objective tracking data, we characterize four clusters of night-time smartphone use.Future plansThe unprecedented size and coverage of theSmartSleep Studyallow for a comprehensive documentation of smartphone activity during the entire sleep span. The study will be expanded by linkage to nationwide registers, which will allow for further investigations into the long-term health and social consequences of night-time smartphone use. We also plan new rounds of data collection in the coming years.STRENGTHS and LIMITATIONS of this studyThe unprecedented size and coverage of theSmartSleep Studyallow for a comprehensive objective and subjective documentation of smartphone activity during the entire sleep span.The data in theSmartSleep Studyare sampled by three different strategies, which allow us to test robustness and validate findings across samples. This aligns with the principles of triangulation, which aims at obtaining more reliable answers to complex research questions through the integration of results from different approaches with different sources of bias.TheSmartSleep Studyis readily available for research projects: the data sources have already been linked, the data have been cleaned and prepared for future analyses.TheSmartSleep Studyis not fully representative of the general population due to the sampling procedures, and we are currently creating weights that can be used in the statistical analysis to compensate for this imbalance.