Healthcare use and costs of functional somatic disorder in Denmark: a population-based cohort study (DanFunD).

Introduction: Studies investigating the economic burden of functional somatic disorder (FSD) in general populations are lacking. The current study incorporated data from a randomly sampled general population to examine healthcare use and costs in FSD using comprehensive national register data. Methods: The study included 9656 adults from the DanFunD general population cohort study. FSD was identified via self-reported questionnaires and verified by diagnostic interviews conducted by a physician. Data on healthcare were sourced from the comprehensive Danish central registries in the period 10 years before and 4 years after DanFunD inclusion. Healthcare use was investigated with Poisson and Zero-inflated Poisson regression models. Healthcare costs were investigated with linear regression models. Analyses comprised sex- and age-adjusted regression models with non-parametric bootstrap resampling (10 000 repetitions). Results: Individuals with FSD used more healthcare facilities and it costed more compared with individuals without FSD. For example, the incidence rate ratio of having used healthcare services for participants with interview-diagnosed severe FSD was 1.62 (95% CI 1.37 to 1.94) in the 10-year period before DanFunD inclusion, and the annual healthcare costs were 1038 € (339 € to 1846 €) higher. Individuals with FSD also had a higher use of healthcare than individuals with other severe physical disease, but in most cases, no differences were found for costs. Conclusions: FSD carries a significant economic burden on society due to increased healthcare use and costs compared with individuals without FSD, and for most, also for individuals with other severe physical disease. Trial registration number: NCT05811663.