(SLC-034) Trends in type 1 diabetes mellitus onset among youth aged 0 to 20 in Korea before and after COVID-19: A nationwide health insurance claims data analysis, 2003-2022

Background: According to anecdotal reports and recent studies, the incidence of type 1 diabetes mellitus(T1DM) has been found to be increasing worldwide, particularly after the COVID-19 pandemic. While accurate data on T1DM incidence is crucial for confirming this trend and informing public health policy, the data remains scarce or limited.

Objectives: This study aims to examine nationwide changes in T1DM incidence among youth aged from 0 to 20 in Korea before and after COVID-19, while considering potential misclassification of with type 2 diabetes mellitus due to limitations in identifying T1DM using health insurance claims data.

Methods: This retrospective cohort study used claims data from the Korea National Health Insurance Service (NHIS) to examine the incidence of T1DM among individuals under 21 years of age. Eligible patients were those with a T1DM diagnosis (ICD-10: E10.x) and at least two insulin prescriptions between 2002 and 2022. To ensure the inclusion of newly diagnosed cases from 2003 onward, individuals diagnosed in 2002 were excluded. The date of the first recorded T1DM diagnosis in each patient’s lifetime was designated as the onset of T1DM. Annual T1DM incidence was estimated as the number of newly diagnosed cases within a given year divided by the total population aged 0-20 for the same year. To evaluate the potential impact of COVID-19 pandemic, an interrupted time series analysis was conducted using 2020 as the intervention point for monthly T1DM incidence. Sensitivity analyses were performed by varying T1DM case definitions. Descriptive statistics were used to summarize patient characteristics. All analyses were conducted using SAS software version 9.4.

Results: A total of 10,610 new T1DM cases from 2003 and 2022 were included in the study with the smallest and largest subgroup comprising 34.5% and 85.3% of the total cases, respectively. The overall annual incidence of T1DM was 5.04 cases per 100,000 population, with peak diagnosis occurring at age 14. Patients had an average of 13 hospital visits within one year before the first diagnosis. The interrupted time series analysis demonstrated T1DM incidence has increased over time (p < 0.001), with additional increases associated with the COVID-19 pandemic (p < 0.001) and the post-pandemic period (p < 0.001), with an estimated annual incidence of 4.42 per 100,000 population in 2003 and 8.20 cases per 100,000 in 2022. Similar trends were observed across all subgroups.

Conclusions: The incidence of T1DM among youth in Korea nearly doubled from 2003 to 2022, with an immediate and sustained increase following the COVID-19 pandemic. These trends were consistent across all subgroups, underscoring the need for enhanced surveillance and targeted public health strategies to address the growing burden of T1DM in Korea.