[Epidemiological characteristics of febrile seizure among children under 6 years old in Ningbo City from 2015 to 2021].

Objective: To describe the epidemiological characteristics and changes of febrile seizure (FS) among children under 6 years old in Ningbo City, Zhejiang Province from 2015 to 2021.

Methods: Based on the Ningbo Regional Health Information Platform, a dynamic cohort was established using vaccination registration information, and the cases of FS were identified by the diagnostic results of Chinese terms or International Classification of Diseases 10th revision (ICD-10) R56.0 code in the electronic medical records. The first visit of FS during the observation period was defined as a new case, and a recurrence case was defined as the case with a visit interval of more than 7 days. The 95% confidence interval (CI) of FS incidence density was calculated by the Poisson distribution.

Results: From January 2015 to June 2020, there were 1.3 million children under 6 years old in Ningbo, with male accounting for 52.87%. The median follow-up time was 2.83 (1.55-4.00) years. During the follow-up period, 12 776 new onset cases had FS, with more males than females, with an overall incidence density of 4.34 (95%CI 4.27-4.40)/1 000 person-years and a recurrence rate of 21.63%. There was a higher incidence density in children who were male, born in Ningbo and of non-mobility. The incidence density of FS was higher in urban areas than in rural and rural-urban fringe areas, and the incidence density was different among districts and counties. The peak density was found in children aged 18-23 months [8.42 (95%CI 8.11-8.74)/1 000 person-years]. From 2015 to 2019, the incidence density increased with calendar year (P_trend < 0.001), and the highest was 5.62 (95%CI 5.43-5.81) /1 000 person-years. The incidence density of FS decreased significantly during the period between 2020 and 2021. The incidence density was higher in winter.

Conclusion: From 2015 to 2019, the overall incidence density of FS in children under 6 years old in Ningbo City presented an increasing trend. More attention should be paid to the health education, the improvement of the health maintenance model, the enhancement of the cognition of FS, the identification and treatment of FS among high-risk population and regions so as to prevent its recurrence and reduce the disease burden during the corona virus disease 2019 (COVID-19) epide-mic.