In Focus
The Danish blood donor study
A platform for donor and public health research in the era of big data
Ole Birger Vesterager Pedersen
University of Copenhagen, Denmark
The Danish Blood Donor Study (DBDS) represents a large, population-based donor cohort. With its three million consecutive archived plasma samples, DBDS ranks among the most sample-dense biobanks globally.
Introduction
Established in 2010, the study was designed to investigate both the health effects of blood donation and broader determinants of health and disease in the general population. By embedding research within the national blood donation infrastructure, DBDS combines cost-efficiency with scientific depth, having enrolled over 175,000 voluntary, healthy blood donors nationwide into this still-expanding cohort1.
All participants are followed through the comprehensive Danish health registers, which provide prospective data on hospital diagnoses, filled prescriptions, vital status, and socioeconomic parameters. The study integrates biological material (>3 million archived plasma samples), extensive questionnaire data (>500,000 responses), and genetic information (>150,000 participants genotyped). Together, these elements create a powerful resource for understanding health, disease mechanisms, and prevention.
From transfusion medicine to population health
DBDS originated from a fundamental question: Is blood donation beneficial or harmful to donor health? Earlier analyses from the Scandinavian Donations and Transfusions (SCANDAT) Database had shown that blood donors live longer than the general population, even after adjustment for confounders. This “Healthy Donor Effect,” similar to the well-known “Healthy Worker Effect,” highlighted the need for dedicated studies to distinguish biological effects of donation from selection bias.
From this starting point, DBDS evolved into a broad public health resource. Because all donors are healthy at the time of donation, the cohort enables pre-diagnostic analyses, studying biomarker trajectories and physiological changes before disease onset. This longitudinal design provides a unique opportunity to observe within-person changes over time, opening new possibilities for early disease detection.
Cohort design and data resources
Blood donors aged 18–75 years are invited to join DBDS at the time of donation after receiving oral and written information and giving consent. The participation rate exceeds 95%, reflecting donors’ altruism and the convenience of integrating research participation into the donation visit.
At each donation, an archive sample is automatically stored, and for participants, 1 mL of plasma is reserved for research, ensuring repeated biospecimens collected at short time intervals. With over three million samples currently available, DBDS is among the most temporally detailed population biobanks worldwide.
Questionnaire data are collected electronically during donation (on donors’ own devices or tablets provided in the blood bank). Approximately once a year, more comprehensive questionnaires are distributed through the national digital mailbox used by all citizens for communication with public authorities. The questionnaires include core items on smoking behaviour, body mass index, and self-reported health, while other topics, such as exercise, diet, gastrointestinal symptoms, allergy, sleep disturbances, and stress, are rotated over time to capture diverse health exposures while keeping completion time short (about 12 minutes on average).
As another unique feature, DBDS also enables re-contact studies, where participants can be invited into new studies based on specific genotypes or phenotypes, facilitating targeted clinical and translational investigations.
Donor health: ensuring safety and well-being
DBDS has yielded important insights into donor health and transfusion safety. Studies have demonstrated that iron deficiency is common among frequent donors, particularly premenopausal women, while genetic variants associated with haemochromatosis protect against iron depletion. Ferritin has been identified as a strong predictor of low haemoglobin, supporting ferritin monitoring as an effective preventive measure2. DBDS has also shown that psychological well-being influences donor retention: donors with better self-reported mental health donate more frequently and remain active longer3. These findings have informed national policies for donor monitoring and counselling, strengthening both donor safety and the sustainability of the blood supply.
Public health research: beyond transfusion medicine
Beyond donor health, DBDS serves as a versatile resource for understanding biological, environmental, and social determinants of disease in a healthy population. An early study showed that obesity increases infection risk, including respiratory, urinary, and skin infections4. Recently, we have described how 47 inflammatory and vascular biomarkers associate with demographic factors5.
In the Staphylococcus aureus Carriage Study, a sub-study to the DBDS, 9,000 donors provided 13,000 nasal swabs, revealing that carriers had a higher risk of redeeming antibiotic prescriptions for skin infections6. Numerous studies have been published within areas such as skin diseases, cardiometabolic diseases, allergy, asthma, and psychiatric diseases. DBDS participates frequently in international genetic consortia with numerous publications in high-ranking journals.
Through these diverse studies, DBDS illustrates how a donor-based platform can generate evidence relevant to general population health, while maintaining the blood service as a cost-effective research infrastructure.
A responsive platform for real-time surveillance
The agility of DBDS was particularly evident during the COVID-19 pandemic. Using the DBDS data infrastructure, the study conducted nationwide seroprevalence surveys in near real time, performing over 250,000 antibody tests. These data provided rapid estimates of seroprevalence and infection fatality rates and informed Danish public health strategies7.
High-dimensional data and future perspectives
DBDS is entering a new era of high-dimensional data. Large-scale proteomic profiling includes thousands of samples analysed for over 3,000 circulating proteins, enabling studies of biomarker trajectories that precede disease onset.
Why donor cohorts matter for Big Data and precision health
The Danish Blood Donor Study demonstrates how national blood services can function as cost-effective, high-impact research platforms. By integrating clinical, biological, and digital data at national scale, donor cohorts enable research not only on transfusion safety but also on the mechanisms of health and disease.
Key advantages of blood donor cohorts:
•Cost-efficiency: Data and samples are collected within existing blood bank operations. •Sequential sampling: Multiple pre-disease samples per individual allow time-resolved analyses rarely feasible elsewhere. •Engagement: Donors are motivated, geographically widespread, and participate repeatedly. •Interoperability: Linkage to national registers enables follow-up even when the donor ceases to be a blood donor.
By maintaining strong partnerships with donors and collaborating broadly across scientific fields, DBDS continues to expand the role of blood services in public health. As we enter the Big Data era, it exemplifies how blood donors are not only lifesavers for patients but also key contributors to understanding and improving the health of future generations.
References
1. Erikstrup C et al. Cohort Profile: The Danish Blood Donor Study Int J Epidemiol. 2023;52:e162–e171. 2. Rigas AS et al. Predictors of iron levels in 14,737 Danish blood donors: results from the Danish Blood Donor Study Transfusion 2014;54:789–96. 3. Didriksen M et al. Experience of loneliness during the COVID-19 pandemic: a cross-sectional study of 50 968 adult Danes Transfusion 2021;61:1479–88. 4. Kaspersen KA et al. Obesity and risk of infection: results from the Danish Blood Donor Study Epidemiology 2015;26:580–89. 5. Kjerulff B et al. Lifestyle and demographic associations with 47 inflammatory and vascular stress biomarkers in 9876 blood donors Commun Med (Lond). 2024;4(1):50. 6. Dinh KM et al. Evaluating infection risk associated with Staphylococcus aureus nasal carriage in blood donors: a prospective multicentre study in Denmark Clin Microbiol Infect. 2025;31(7):1180-1186. 7. Erikstrup C et al. Seroprevalence and infection fatality rate of the SARS-CoV-2 Omicron variant in Denmark: A nationwide serosurveillance study Lancet Reg Health Eur. 2022;21:100479.
