Prevalence of chronic conditions among children and adolescents-register data and self-reports

The purpose of this study is to estimate the prevalence of chronic health conditions (CHCs) among children and adolescents in Denmark using data from national population registers and survey data from self-reports. The data originated from two sources: (1) the Danish national registers and (2) two nationally representative surveys. A 20% random sample of all children born between 1994 and 2013 (N = 263,864) was drawn from the Danish national registers and included records of in- and out-patients in public hospitals, in primary health care or indicated prescriptions. Self-reported health conditions were obtained from the two nationally representative surveys (N = 70,534). Chronic conditions were classified by experienced clinicians across the range of physical and mental health conditions in the International Classification of Diseases, 10th revision (ICD-10). In the register data, the overall prevalence of CHCs increased with age in both sexes, from 9.3% to 14.6% among 1-10-year-olds and from 18.3% to 22.0% among 11-20-year-olds, mainly due to an increased frequency of mental disorders with age. The prevalence of self-reported CHCs was 28.4% among 11-15-year-olds, 14.6% of whom reported being affected in their daily lives. Among 16-20-year-olds, the prevalence of self-reported CHCs was 34.2%, and 15.3% reported being affected in their daily lives.

The inclusion of both register-based and survey data allowed the study to capture different groups of children and adolescents. Furthermore, the choice of method used to estimate the prevalence of CHCs depends strongly on the data source, the case definition, and the context of the healthcare system.

• The prevalence of chronic health conditions (CHCs) found among children and adolescents varies due to methodological variability and use of definitions. • Using national registries, this study has explored the prevalence of physical and mental health conditions across all ICD-10 diagnoses among children and adolescents referred to a hospital.

• In the register data, the prevalence of CHCs varied between 9.3% and 18.3% in the child population; in the youth population, 22% were diagnosed with a condition classified as chronic. • Self-reported data from 11-15-year-olds and 16-20-year-olds showed prevalences of 28.4% and 34.2%, respectively, including CHCs not necessarily exceeding the threshold of clinical referral.