The Changing Incidence Of Childhood-Onset Type 1 Diabetes In Wales: Effect Of Gender And Season At Diagnosis And Birth

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 deter-mine 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 center dot 3 cases/year/100,000 chil-dren 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 diet-ary supplementation with vitamin D might further reduce the incidence of type 1 diabetes. (c) 2021 Elsevier B.V. All rights reserved.