The Danish National Survey of Diet and Physical Activity (DANSDA) 2021-2024: Study Design and Participants...

Background: The Danish National Survey of Diet and Physical Activity (DANSDA) is Denmark's national dietary surveillance system, providing population-level data to support evidence-based government advisory tasks and policymaking, research, and education. Methods: DANSDA 2021-2024 is a cross-sectional survey based on a simple random sample of citizens aged 4-80 years from the Danish Civil Registration System. Home visits included structured interviews covering socio-economic status, family composition, ethnicity, lifestyle behaviors and attitudes, health and non-communicable diseases, dietary supplement use, and measurements of anthropometrics and blood pressure. Dietary intake was recorded using a digital or paper-based seven-day food record and a food frequency questionnaire. Physical activity was measured with a pedometer and a seven-day step diary. Participants aged 40-70 years were offered blood sampling for glucose and lipid analyses. Results: A total of 4223 individuals participated, with 3824 providing valid food records (97.4% were digital). The response rate was 26.3%. The overall underreporting rate was 24%. The sample was skewed by age, education, income, household type, and region; these variables and sex were used to generate weighting factors. Nearly 1000 blood samples were analyzed for glucose and lipids, with surplus material stored in a biobank. Conclusions: DANSDA 2021-2024 provides comprehensive data on diet, physical activity, anthropometry, blood pressure, and blood glucose and lipids. Despite declining response rates and underrepresentation of individuals with lower education and income, weighting procedures support its continued use for national monitoring and research. Strengthening participation and representativeness should be a priority in future survey cycles.