Type 1 Diabetes Mellitus in the First Years of Life - Onset, Initial Treatment, and Early Disease Course.

Objective: This study investigated the onset and the choice of treatment in children with very early onset of type 1 diabetes mellitus (T1D).

Methods: The study included 5,763 patients from the German Diabetes Patient Follow-up registry with onset of T1D in the first 4 years of life from January 2010 - June 2022. The analysis included diabetes-specific parameters, anthropometric data, and mode of treatment at onset, within the first and second year of T1D. Three groups were compared according to age at onset (G1: 223 patients 6-<12 months, G2: 1519 patients 12-<24 months, G3: 4001 patients 24-48 months).

Results: In 12.3% of all cases in childhood and adolescence, the incidence of diabetes in the first 4 years of life was rare. At the onset, clinical status was worse and diabetic ketoacidosis (DKA) rates were higher in G1 and G2 (52.3% and 46.5%, respectively) compared to G3 (27.3% (p<0.001)). G1 and G2 were significantly more likely to be treated with insulin pump therapy (CSII) 2 years after onset (98.1% and 94.1%, respectively)) compared to G3 (85.8%, p<0.001). Median HbA1c after 2 years did not differ between groups (G1: 7.27% (56.0 mmol/mol), G2: 7.34% (56.7 mmol/mol) and G3: 7.27% (56.0 mmol/mol)) or when comparing CSII vs MDI. The rate of severe hypoglycemia (SH) and DKA during the first 2 years of treatment did not differ among the three groups, ranging from 1.83-2.63/100 patient-years (PY) for DKA and 9.37-24.2/100 PY for SH. Children with T1D under 4 years of age are more likely to be diagnosed with celiac disease but less likely to have thyroiditis than older children with T1DM.

Conclusions: Young children with T1D had high rates of DKA at onset and were predominantly treated with insulin pump therapy during the first 2 years. The median HbA1c for all three groups was<7.5% (58 mmol/mol) without increased risk of SH or DKA. The use of continuous glucose monitoring (CGM) was not associated with lower HbA1c in children under 48 months.