The German National Cohort (NAKO): Design, current state, and further follow-up data collection

The German National Cohort (NAKO) is the largest population-based cohort study in Germany and provides a central resource for epidemiologic research. NAKO aims to investigate the development and aetiology of diseases, and to identify risk factors and enhance early detection and prevention of diseases with a focus on diabetes, cancer, cardiovascular, pulmonary, neurological, psychiatric, and infectious diseases. Between 2014 and 2019, overall 205,415 participants aged 20-74 years were recruited and examined at 18 study centres across Germany. During their visit to the study centre, they participated in an extensive examination programme including a face-to-face interview, self-administered, computer-based questionnaires, broad biomedical examinations (e.g., blood pressure, electrocardiograms, oral glucose tolerance tests) and provision of bio-samples (blood, urine, stool, saliva, nasal swabs). In addition, a subgroup of 30,861 participants received whole-body Magnet Resonance Imaging (MRI) with a focus on brain, heart, the musculoskeletal system, and body fat distribution. All study participants are re-invited for examinations at the study centres at 4-5 year intervals. The programme of the first re-examination is similar to the baseline programme in order to detect changes in risk factor profiles and in vascular, cardiac, metabolic, neurocognitive, pulmonary and sensory function. By 31.03.23, 100,822 participants were re-examined, including 14,950 with MRI re-examination. A third examination will start in 2024. Data collection is standardized, and central quality control and data cleaning is performed. For more complex data (e.g., echocardiography, accelerometry), competence units process the data and derive variables on exposure, functions, and disease. Due to its large sample size, the in-depth examination programme and the longitudinal design, NAKO provides an excellent source for better understanding of determinants for health and disease at the population level.