The Danish National Health Survey 2023: study design and participant characteristics.

Aim: To describe the design of the Danish National Health Survey (DNHS) 2023, participants' demographic characteristics and differences in demographic and selected health-related characteristics between respondents invited by web-mode and paper-mode.

Methods: A sample of 25,000 residents in Denmark aged 16 years or above was invited to participate in the DNHS 2023 using a mixed-mode approach (web/paper mode). Web-mode invited were additionally invited to participate in an accelerometer study. The self-administered questionnaire included 83 questions about health, health behaviour and morbidity. Descriptive statistics were used to describe characteristics associated with response and invitation mode.

Results: The response proportion was 40.8%. Non-response was more frequent among men, individuals of the youngest age groups, individuals with non-Western backgrounds, unmarried and individuals from densely populated areas. The response proportion was higher among web-mode invited (42.0%) than paper-mode invited (22.6%). Paper-mode invited respondents were more often women, aged 80 years or older, and widowed compared with web-mode invited respondents.

Conclusions: The DNHS 2023 is a national health survey including adult residents in Denmark. Non-response was more pronounced among some subgroups; however, calibrated weights were calculated to minimise non-response bias. The survey is essential for public health surveillance and can be used in health planning and policy development. Furthermore, the data from the survey can be used for research on the population's health and health behaviour. For future waves of the DNHS, it should be considered whether resources should be used to invite people unsubscribed from digital-post due to the low response proportion.