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.

Background: The incidence of type 1 diabetes has increased worldwide whereas a long-term trend for pediatric type 1 diabetes has remain elusive in Japan. Objective: This study aimed to investigate the incidence and secular trend of pediatric type 1 diabetes before and during the COVID-19 pandemic from 1999 to 2021 in Oita Prefecture, Japan. Subjects: We investigated the increase in numbers of newly diagnosed patients with type 1 diabetes aged <15 years from1999 to 2021. Method: We surveyed the medical information from hospitals in Oita and Oita Prefecture database in Japan. Result: The incidence of type 1 diabetes in those aged <15 years increased annually by 5.3% in all children, especially by 8.1% in boys aged 10–14 years during the past 23 years. The average incidence rate of 3.9/100,000/year was almost consistent with the previous report from Asian countries. However, no significant change was found in the increasing incidence trend of type 1 diabetes before and during the COVID-19 pandemic. Conclusion: The incidence of pediatric type 1 diabetes in Japan has significantly increased over the past 23 years, which is consistent with a worldwide trend. No significant increasing trend was observed during the past 2 years during the COVID-19 outbreak.

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