Long-term trends of pediatric type 1 diabetes incidence in Japan: before and during the COVID-19 pandemic years (1999-2021)

Abstract 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.