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Journal of Peking University (Health Sciences) ›› 2025, Vol. 57 ›› Issue (3): 584-591. doi: 10.19723/j.issn.1671-167X.2025.03.024

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

Guangxu LIU1, Liang ZHANG2, Houyu ZHAO1, Siwei DENG1, Junting YANG1, Ning LI2, Rui MA2, Yan HE3, Guozhang XU2, Zhike LIU1,*(), Siyan ZHAN1,*()   

  1. 1. Department of Epidemiology and Biostatistics, Peking University School of Public Health, Beijing 100191, China
    2. Ningbo Municipal Center for Disease Control and Prevention, Ningbo 315010, Zhejiang, China
    3. Ningbo Women & Children's Hospital, Ningbo 315012, Zhejiang, China
  • Received:2022-08-03 Online:2025-06-18 Published:2025-06-13
  • Contact: Zhike LIU, Siyan ZHAN
  • Supported by:
    the National Natural Science Foundation of China(91846303); the Special Project for Director, China Center for Evidence Based Traditional Chinese Medicine(2020YJSZX-2)

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Abstract:

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 (Ptrend < 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.

Key words: Febrile seizures, Incidence density, Epidemiological characteristics, Dynamic cohort, Children

CLC Number: 

  • R720.597

Table 1

Basic demographic characteristics of children under 6 years old in Ningbo City from 2015 to 2021"

Characteristics variables Total (n=1 302 937) Non-FS children (n=1 290 161) FS children (n=12 776) U/χ2 a P
Follow-up/years, M (P25, P75) 2.83 (1.55, 4.00) 2.81 (1.55, 4.00) 3.97 (3.03, 4.84) 77.0b < 0.000 1
Gender, n (%) 414.7 < 0.000 1
    Female 614 075 (47.13) 609 179 (47.22) 4 878 (38.21)
    Male 688 855 (52.87) 680 957 (52.78) 7 898 (61.79)
Birth year, n (%) 3 721.3 < 0.000 1
    2009 52 503 (4.03) 52 474 (4.07) 29 (0.23)
    2010 97 372 (7.48) 97 180 (7.53) 192 (1.50)
    2011 114 688 (8.80) 114 165 (8.85) 523 (4.09)
    2012 127 890 (9.82) 126 776 (9.83) 1 114 (8.72)
    2013 123 135 (9.45) 121 577 (9.42) 1 558 (12.19)
    2014 139 110 (10.67) 136 920 (10.61) 2 190 (17.14)
    2015 124 730 (9.57) 122 794 (9.52) 1 936 (15.15)
    2016 135 426 (10.39) 133 393 (10.34) 2 033 (15.91)
    2017 124 524 (9.56) 122 843 (9.52) 1 681 (13.16)
    2018 103 732 (7.96) 102 772 (7.97) 960 (7.51)
    2019 93 662 (7.19) 93 178 (7.22) 484 (3.79)
    2020 66 165 (5.08) 66 089 (5.12) 76 (0.59)
City of birth, n (%) 756.6 < 0.000 1
    Ningbo outside 428 490 (32.88) 425 742 (33.00) 2 748 (21.51)
    Ningbo 873 107 (67.01) 863 094 (66.90) 10 013 (78.37)
    Missing 1 340 (0.10) 1 325 (0.10) 15 (0.12)
Mobility population, n (%) 167.9 < 0.000 1
    No 972 391 (74.63) 962 222 (74.58) 10 169 (79.59)
    Yes 330 546 (25.37) 327 939 (25.42) 2 607 (20.41)
Location, n (%) 95.0 < 0.000 1
    Urban 763 701 (58.61) 755 716 (58.58) 7 985 (62.5)
    Urban-rural fringe 309 936 (23.79) 307 319 (23.82) 2 617 (20.48)
    Rural 227 820 (17.49) 225 661 (17.49) 2 159 (16.90)
    Missing 1 480 (0.11) 1 465 (0.11) 15 (0.12)
District, n (%) 903.4 < 0.000 1
    Yuyao 171 664 (13.17) 170 314 (13.2) 1 350 (10.57)
    Beilun 128 216 (9.84) 126 985 (9.84) 1 231 (9.64)
    Fenghua 66 982 (5.14) 65 952 (5.11) 1 030 (8.06)
    Ninghai 98 411 (7.55) 97 627 (7.57) 784 (6.14)
    Cixi 251 111 (19.27) 249 186 (19.31) 1 925 (15.07)
    Jiangbei 69 471 (5.33) 68 738 (5.33) 733 (5.74)
    Haishu 90 916 (6.98) 89 920 (6.97) 996 (7.8)
    Xiangshan 70 338 (5.40) 69 900 (5.42) 438 (3.43)
    Yinzhou 271 894 (20.87) 268 861 (20.84) 3 033 (23.74)
    Zhenhai 77 081 (5.92) 75 858 (5.88) 1 223 (9.57)
    Missing 6 853 (0.53) 6 820 (0.53) 33 (0.26)

Table 2

Population characteristics of the FS incidence density among children under 6 years old in Ningbo City from 2015 to 2021"

Variable Number of FS episodes, n (%)a Follow-up(/person-years) Incidence density (95%CI)(/1 000 person-years)
Total 16 326 (100.00) 3 765 767.35 4.34 (4.27-4.40)
Gender
    Female 6 134 (37.57) 1 776 810.55 3.24 (3.13-3.35)
    Male 10 192 (62.43) 1 988 941.25 4.75 (4.67-4.84)
Birth city
    Ningbo outside 3 361 (21.59) 1 038 704.37 3.24 (3.13-3.35)
    Ningbo 12 944 (79.28) 2 722 824.45 4.75 (4.67-4.84)
Mobility population
    No 13 072 (80.06) 2 796 648.95 4.67 (4.59-4.76)
    Yes 3 254 (19.94) 969 118.40 3.36 (3.24-3.48)

Figure 1

Age distribution characteristics of FS incidence density among children under 6 years old in Ningbo City from 2015 to 2021 FS, febrile seizure."

Table 3

Regional distribution characteristics of the FS incidence density among children under 6 years old in Ningbo City from 2015 to 2021"

Location Number of FS episodes, n (%) Follow-up(/person-years) Incidence density (95%CI)(/1 000 person-years)
Urban 10 329 (63.33) 2 224 472.86 4.64 (4.55-4.73)
Urban-rural fringe 3 289 (20.16) 891 344.26 3.69 (3.57-3.82)
Rural 2 692 (16.51) 646 612.06 4.16 (4.01-4.32)

Figure 2

Diagram of regional distribution of the incidence density of FS among children under 6 years old in Ningbo City from 2015 to 2021 (/1 000 person-years) This figure was drawn by ArcGIS software version 10.6. FS, febrile seizure."

Figure 3

Temporal distribution of incidence density of FS among children under 6 years old in Ningbo City from 2015 to 2021 FS, febrile seizure."

Figure 4

Time distribution of FS incidence among children under 6 years old in Ningbo City from 2015 to 2020 The data of 2021 were excluded due to the incompleteness. A, distributed by month; B, distributed by season. FS, febrile seizure."

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