The German National Cohort (NAKO): Overview and Current State

Abstract The presentation aims to give an overview of design, methods and first results of the German National Cohort (NAKO), the largest cohort study in Germany. NAKO is a multidisciplinary, population-based cohort study that provides a central resource for population-based epidemiologic research. NAKO aims to investigate the development and aetiology of diseases, identify risk factors and enhance early detection and prevention of diseases with a focus on diabetes, cancer, cardiovascular, pulmonary, neuropsychiatric and infectious diseases. Between 2014 and 2019, a total of 205,415 persons aged 20 - 74 years were recruited and examined at 18 study centres across Germany. The participants were invited to their local study centre to participate in a face-to-face interview, complete self-administered computer-based questionnaires, undergo a battery of biomedical examinations, and provide various biosamples. In addition, whole-body Magnet Resonance Imaging (MRI) was performed in 30,861 participants on dedicated 3 Tesla MRI scanners at 5 study centres. In 4-5 year intervals, all study participants are re-invited for examinations at the study centres. The programme for the first re-examination (including MRI scanning) was similar to the baseline programme. Thereby, longitudinal information on changes in risk factor profiles and in vascular, cardiac, metabolic, neurocognitive, pulmonary and sensory function is collected. During the COVID-19 pandemic, questions on pandemic-related aspects including the history of infection, severity and long-term health impacts of COVID-19 were added to the examination programme. Since October 2018, 77,896 participants have been re-examined, including 11,382 with additional MRI examination. A supplemental COVID-19 questionnaire was completed by 161,849 participants of NAKO during the first COVID-19-related lockdown in Spring 2020.

This workshop aims to give an overview of design, methods and first results of the largest cohort study in Germany: the German National Cohort (NAKO).This organized session will consist of one overview presentation and three presentations on selected topics: mental disorders, COVID-19, and Magnetic Resonance Imaging (MRI) in the NAKO.NAKO is a multidisciplinary, population-based cohort study that provides a central resource for population-based epidemiologic research.NAKO aims to investigate the development and aetiology of diseases, 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 persons aged 20-74 years were recruited and examined at 18 study centres across Germany.During their visit to the study centre, they participated in a face-to-face interview, completed self-administered, computer-based questionnaires, underwent a battery of biomedical examinations, and provided various biosamples.In addition, whole-body Magnet Resonance Imaging (MRI) was performed on 30,861 participants using dedicated 3 Tesla MRI scanners at 5 study centres.The whole-body MRI protocol focuses on brain and cardiac structures, musculoskeletal system and body fat distribution.In 4-5 year intervals, all study participants are re-invited for examinations at the study centres.The programme for the first re-examination (including MRI scanning) was similar to the baseline programme.Thereby, longitudinal information on changes in risk factor profiles and in vascular, cardiac, metabolic, neurocognitive, pulmonary and sensory function is collected.Since October 2018, 77,896 participants have been re-examined, including 11,382 with additional MRI examination.A supplemental COVID-19 questionnaire collected data on 161,849 participants of NAKO during the first COVID-19related lockdown in Spring 2020.This survey started on 30 April 2020 and ended on 30 June 2020.The questionnaire included questions on general state of health, Sars-CoV-2 symptoms and test results, and on changes in behavioural, psychosocial and socioeconomic factors as well as social contacts and occupational situation during the pandemic.Thus, psychological and socioeconomic effects of the pandemic situation can be addressed.Moreover, questions on pandemic-related aspects including the history of infection, severity and long-term health impacts of COVID-19 were added to the regular study programme in the study centres as of July 2021.The longitudinal design of NAKO provides the unique opportunity to compare the participants' situation before and during the pandemic.The presentations describe the main design of the NAKO and exemplary results of main research questions, e. g., on mental health, association of occupational factors with COVID-19, and MRI findings.

Key messages:
The workshop introduces the design and collected data of the NAKO to foster collaboration between scientists, enabling further harmonization of data collection between large cohort studies.
The workshop aims to facilitate (future) joint scientific exploitation of this unique epidemiological resource of population-based data.

Background:
The mental health status of populations (public mental health) and its effect on societies has gained considerable attention in recent years, especially during the current pandemic.The measurement of depressive symptoms is at core of the assessment of mental health.The detailedness of this assessment defines the range of public mental health problems that can be answered.).These instruments include different time periods and interpretations.Associations between these depression outcomes and age, gender and education are analysed in linear and logistic regression models.

Results:
A lifetime physician's diagnosis of depression was reported by 14.7% of participants with considerable regional variation and almost 50% of this group received treatment within the last 12 months.Based on PHQ-9 7.9% of the participants were classified as depressive according to the dimensional assessment (score10) and 3% of them as having a major depression subtype.In contrast 32.8% screened positive based on the MINI and 15.4% of those receiving the full MINI had a diagnosis MDD.Associations with important socioeconomic determinants for these different depression outcomes will be reported.

Conclusions:
The large NAKO sample size and the detailed assessment of depression symptoms and status enables the analysis of a broad range of public mental health questions.The analysis of depression frequencies and the distribution of depressive symptoms allow the establishment of population references.

Background:
Numerous studies reported an increase in mental disorders during the COVID-19 pandemic, but the specific causes for this increase are unclear.We therefore investigate whether pandemic-related occupational and financial changes (e.g., reduced working hours, working from home, financial losses) were associated with increased symptoms of depression and anxiety compared with the situation before the pandemic.

Methods:
We analyzed data from the German National Cohort Study (NAKO).Between May and November 2020, 161,849 participants answered questions on their mental state and social circumstances.Responses were compared with data from the baseline survey before the pandemic (2014-2019).Linear fixedeffects models were used to determine whether individual changes in the symptoms of depression (PHQ-9) or anxiety (GAD-7) were associated with occupational/financial changes (controlling for covariates).

Results:
A pronounced increase in symptoms was observed among those who became unemployed during the pandemic (+ 1.16 points on the depression scale, 95% confidence interval [0.91; 1.41], range 0-27).Increases were also seen for reduced working hours without short-term working allowance, increased working hours, working from home, insecurity regarding employment, and financial strain.The deterioration in mental health was largely statistically explained by the occupational and financial changes investigated in the model.

Conclusions:
Depressive symptoms and anxiety disorders increased in the study population during the first year of the COVID-19 pandemic and occupational and financial difficulties were an essential contributory factor.These strains should be taken into account both in the care of individual patients and in the 15th European Public Health Conference 2022 Methods: Between 2014 and 2019 the German National Cohort (NAKO) recruited 205,000 participants aged 20-70 years into the baseline examination in 18 study centers.Depression and depressive symptoms were assessed by different instruments including a lifetime diagnosis of depression and current treatment, the Major Depressive Disorder (MDD) section of the Mini-International-Neuropsychiatric-Interview (M.I.N.I. 5.0) and the depression scale of the Patient Health Questionnaire (PHQ-9