The changing incidence of childhood-onset type 1 diabetes in Wales: Effect of gender and season at diagnosis and birth

Diabetes Res Clin Pract. 2021 May:175:108739. doi: 10.1016/j.diabres.2021.108739. Epub 2021 Mar 9.


Aims: Determinants of the changing incidence of childhood-onset type 1 diabetes remain uncertain. We determined the recent time-trend of type 1 diabetes incidence in Wales and explored the role of vitamin D by evaluating the influence of season both at diagnosis and at birth.

Methods: Data from all Welsh paediatric units 1990-2019, and from primary care to determine ascertainment.

Results: Log-linear modelling indicated a non-linear secular trend in incidence with peak and subsequent decline. The peak occurred around June 2010: 31∙3 cases/year/100,000 children aged < 15y. It occurred earlier in children younger at diagnosis and earlier in boys. There were more cases in males aged <2y and >12y but more in females aged 9-10 y. More were diagnosed in winter. Also, children born in winter had less risk of future diabetes.

Conclusions: The risk of developing type 1 diabetes before age 15y in Wales is no longer increasing. The data on season are consistent with a preventative role for vitamin D both during pregnancy and later childhood. Metereological Office data shows increasing hours of sunlight since 1980 likely to increase vitamin D levels with less diabetes. Additional dietary supplementation with vitamin D might further reduce the incidence of type 1 diabetes.

Keywords: Aetiology; Childhood; Incidence rate; Type 1 diabetes; Vitamin D.

MeSH terms

  • Adolescent
  • Child
  • Child, Preschool
  • Diabetes Mellitus, Type 1 / epidemiology*
  • Female
  • Gender Identity
  • Humans
  • Incidence
  • Male
  • Parturition / physiology*
  • Pregnancy
  • Prospective Studies
  • Seasons
  • Wales / epidemiology