medwireNews: Researchers report that having type 1 diabetes may affect children’s brain growth and cognitive development, with persistent hyperglycemia the most likely culprit.
The team previously reported that gray matter and white matter growth rates were significantly lower over 18 months in 144 children with type 1 diabetes than in 72 age-matched controls, particularly in the parietal–occipital cortical regions. In the frontal–temporal regions the opposite was true – with the cases having larger volumes than the controls.
The children were aged between 4 and 10 years (average 7 years) and had been diagnosed with type 1 diabetes at least 6 months previously (median duration 2.5 years). They underwent magnetic resonance imaging and cognitive testing at baseline and 18 months.
After a pause due to a gap in funding, the children were reassessed approximately 4.5 years after baseline. They were aged an average of 11 years at this point, and their average glycated hemoglobin (HbA1c) had not appreciably changed over the time, from 7.9% at baseline to 8.0% at follow-up.
At this time, the researchers found that the children with type 1 diabetes had significantly smaller volumes of total and subcortical gray and white matter than controls, with this being “particularly pronounced” in cortical regions involved in sensory processing and cognition.
Also by this third timepoint, the basal ganglia (which is involved in the regulation of motor function, memory, language, and social behavior) had become significantly smaller in the diabetes patients compared with the controls.
Presenting the data to the media at the 79th ADA Scientific Sessions in San Francisco, California, USA, Nelly Mauras (Nemours Children’s Health System, Jacksonville, Florida, USA) revealed that the differences between the children with diabetes and the control participants were significantly associated with lifetime hyperglycemia exposure. HbA1c was measured every 3 months between baseline and 18 months and again at the later follow-up, and hyperglycemia exposure was defined as the average amount of the HbA1c area under the curve that exceeded 6.0%.
Furthermore, the team found that these children with diabetes had significantly lower scores for full-scale and verbal IQ and vocabulary than the control participants, and this was again associated with lifetime hyperglycemia.
Mauras said that the “striking” finding to her team was the association with hyperglycemia. “So this notion that parents have that they’d rather [avoid hypoglycemia] because low has been the biggest fear we’ve had, and legitimately so, because it impairs [short-term] cognition – we already know that.
“But for us it has been very consistent,” she said, with hyperglycemia, regardless of the means of measuring it, associated with structural changes and cognition. By contrast, hypoglycemia was not associated with these changes, whereas glycemic variability was associated with most of the same changes as hyperglycemia was.
“So I think it gives you one more reason to control [blood sugar] better,” said Mauras, “but also goes back to guidelines, I think: are hemoglobin A1cs in the mid-7s enough to prevent these kinds of changes?”
She stressed that the changes seen “have not translated into a functional outcomes of poor academic performance – at least not yet.”
But Mauras stressed that the changes are real and persistent across more than 4 years. “So whether or not, given time, we will see bigger functional changes I think remains to be seen and that’s why we have to continue to follow these patients.”
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ADA Scientific Sessions, San Francisco, California, USA: 7–11 June