Temporal Trends in the Epidemiology of Eating Disorders Between 2000 and 2022: A Danish Register Study of Their Incidence and Comorbidities.

backgroundEating disorders are debilitating illnesses that often co-occur with other psychiatric disorders and somatic diseases. Evidence indicates that the incidence of eating disorders has been increasing. We first examine the landscape of EDs over time, including the COVID-19 period, via assessing the incidence of anorexia nervosa (AN), bulimia nervosa (BN), and other eating disorders (OED) in Denmark. We additionally map the impact of eating disorders by assessing their prevalence and comorbidities.

methodsDiagnosed eating disorder cases were identified from the Danish National Patient Register from 1995 to 2022. We calculated age- and sex-specific incidence rates for each year. We additionally calculated prevalence for the years 2000, 2010, and 2022 and identified comorbidities via primary or secondary ICD-10 diagnoses from inpatient and outpatient hospital contacts and prescription medication data from the Danish National Prescription Registry. Associations between eating disorders and ICD-10 diseases and prescription medication were investigated with logistic regression models.

resultsThe incidence of eating disorders increased over the study time in younger age groups for both sexes, particularly for AN and OED, whilst BN diagnoses showed a declining incidence rate (IR) from 2017 onwards. Evidence for increased incidence rates during and following the COVID-19 pandemic was strongest for AN and OED in females aged 10-14 (respectively a 35.5% increase in IR for AN and 57.1% for OED between 2019 and 2021). All eating disorders showed high levels of comorbidities with both psychiatric and somatic illnesses. For example, BN (OR = 23.37, 95% CI: 17.52-31.16) and OED (OR = 19.09, 95% CI: 14.89-24.48) were associated with subsequent abuse of non-dependence-producing substances, and AN was associated with diseases of the circulatory system (OR = 1.88, 95% CI: 1.77-2.01), with diagnoses occurring on average almost 1 year after AN. DISCUSSION: The incidence of AN and OED has increased in the last 22 years in Denmark. Increased incidence in younger age groups after 2020 is likely due to psychosocial challenges and heightened vulnerability to mental health difficulties during the COVID-19 pandemic. Low prevalence of EDs in males may demonstrate poor identification and underdiagnosis. EDs have high public health impact given their increasing prevalence and breadth of identified somatic and psychiatric comorbidities.