Long-term trends of pediatric type 1 diabetes incidence in Japan before and after the COVID-19 pandemic

Type 1 diabetes incidence has increased worldwide, although the long-term trends on pediatric type 1 diabetes in Japan remain elusive. To investigate the incidence and secular trend of pediatric type 1 diabetes from 1999 to 2021, including the coronavirus disease 2019 (COVID-19) pandemic years, in Oita Prefecture, Japan. We investigated the number of newly diagnosed patients with type 1 diabetes aged < 15 years from 1999 to 2021. We surveyed hospital databases in Oita Prefecture in Japan. The type 1 diabetes incidence in children aged < 15 years increased annually by 5.3% among all children, especially in boys aged 10-14 years by 8.1%, over the past 23 years. The average incidence rate of 3.9/100,000/year was nearly consistent with the previous reports on Asian countries. No significant change was found in the increasing incidence trend of type 1 diabetes before and during the COVID-19 pandemic. The incidence of pediatric type 1 diabetes has significantly increased over the past 23 years in Oita Prefecture, Japan, which is consistent with the worldwide trend.