Cohort profile: CROSS-TRACKS – a population-based open cohort across healthcare sectors in Denmark
Authors: Riis Anders Hammerich , Kristensen Pia Kjær , Petersen Matilde Grøndahl , Ebdrup Ninna Hinchely , Lauritsen Simon Meyer , Jørgensen Marianne Johansson 
Published: May 2020

AbstractPurposeThis paper describes the open cohort CROSS-TRACKS, which was set up in Denmark in 2015. The cohort comprises population-based data from primary care, secondary care, and national registries. In addition, the paper outlines the new research opportunities provided by the cohort; the possibility to study patient pathways and transitions across sectors while adjusting for sociodemographic characteristics. The new data source is especially interesting for studies of potentially preventable admissions and readmissions.ParticipantsA total of 221,283 individuals resided in the four Danish municipalities that constituted the catchment area of Horsens Regional Hospital in 2012–2018. A total of 96% of the population used primary care, 35% received at least one transfer payment, and 66% was in contact with a hospital at least once in the period. Additional clinical information is available for hospital contacts (eg alcohol intake, smoking status, body mass index, and blood pressure). A total of 27% (n=9,986) of individuals aged ≥65 years had at least one potentially preventable hospital admission, and 69% (n=6,881) of these individuals had more than one.Findings to dateThe cohort is currently used for research projects in epidemiology and artificial intelligence. These projects comprise a prediction model for potentially preventable hospital admissions, a clinical decision support system based on artificial intelligence, prevention of medication errors in the transition between sectors, health behaviour and sociodemographic characteristics of men and women prior to fertility treatment, and a recently published study applying machine learning methods for early detection of sepsis.Future plansThe CROSS-TRACKS cohort will be expanded to comprise the entire Central Denmark Region consisting of 1.3 million residents. The cohort can provide new knowledge on how to best organise interventions across healthcare sectors and prevent potentially preventable hospital admissions. Such knowledge would benefit both the individual citizen and society as a whole.Strengths and limitations of this studyThe CROSS-TRACKS cohort is a population-based open cohort containing routinely collected data from both primary and secondary care combined with sociodemographic register data.The cohort is readily available for research projects: the data sources have already been linked, patient pathways have been identified, and data have been remodelled and prepared for cutting-edge use of artificial intelligence and to enable easier and simpler querying across source systems.The cohort is currently limited to the catchment area of Horsens Regional Hospital, but it covers both urban and rural areas and it has a total population of 221,283 individuals by 2018.The cohort will be expanded to include additional catchment areas in the Central Denmark Region, comprising a total population of 1.3 million individuals.The cohort offers new opportunities for health research by tracking the patients’ pathway across healthcare sectors to provide new knowledge on the best way to organise future interventions.