Objectives: Neurocognitive functions of children with type 1 diabetes mellitus (T1D) are reported to be poorer than those of healthy peers. The aim was to investigate the effects of age of onset of diabetes, metabolic control, and type of insulin regimen on neurocognitive functions in children and adolescents with T1D.

Methods: Forty-seven children aged 6-18 years, with T1D for at least five years, were included. Children with a known psychiatric disorder or chronic diseases other than T1D were excluded. Intelligence via the Wechsler children's intelligence scale (WISC-R), short-term memory via the audio-auditory digits form B (GISD-B) test, visual motor perception via the Bender Gestalt test, and attention via the Moxo continuous attention and performance test, timing, hyperactivity, and impulsivity (Moxo-dCPT) were assessed.

Results: Compared with the T1D group, healthy controls had higher scores in terms of verbal intelligence quotient (IQ), performance IQ, and total IQ mean scores on WISC-R (p=0.01, p=0.05 and p=0.01, respectively). On the MOXO-dCPT test, the T1D group had higher impulsivity compared to the control group (p=0.04). Verbal IQ was better in the moderate control group than in the poorer metabolic control (p=0.01). Patients with no history of diabetic ketoacidosis (DKA) had higher performance, verbal and total intelligence scores than the group with history of DKA.

Conclusions: Poor metabolic control and a history of DKA in children with T1D adversely affected neurocognitive functions. It would be beneficial to consider the assessment of neurocognitive functions in T1D and to take the necessary precautions in follow-up.