Non-participation in a health examination survey in a rural-provincial area of Denmark – results from the Lolland-Falster Health Study (LOFUS)

Background: Lolland-Falster Health Study (LOFUS) was a health examination survey that included self-administered questionnaires, clinical examinations, and the collection of biological samples, undertaken in 2016–2020 in a rural, socioeconomically deprived area with the lowest life expectancy in Denmark. The aim of this study was to examine the determinants of non-participation in LOFUS to evaluate the extent to which LOFUS data reflected the general population of the area. Methods: LOFUS invited randomly selected subjects together with their entire household. As determinants of non-participation, we analyzed age, sex, municipality of residency, citizenship, residency status, socioeconomic status, invitation type, and year of invitation. Relative risk regression was used to estimate the association between determinants and non-participation rate, mutually adjusted for other determinants. Results: In total, 53,313 subjects were invited of whom 18,949 (36%) participated. In the multivariable analysis, men had a 3% higher non-participation rate than women; subjects with citizenship other than Danish had a 3% higher non-participation rate than Danes. In-migrants had 6% higher non-participation than long-term residents. Compared with self-supported subjects aged 30–64, both publicly supported subjects of this age and younger and older subjects had higher non-participation rates: 16%, 16%, and 13%, respectively. Compared with self-supported, long-term residents, publicly supported in-migrants had 23% higher non-participation. Conclusions: Only about one third of subjects invited to LOFUS participated. Yet, this is a relatively high participation rate compared with other recent health examination surveys in Denmark. Furthermore, there was a relatively flat social gradient in the non-participation rate across the studied determinants.