Research

Diabetes a cognitive risk for developing brain


Cognitive function in young adults with diabetes is below average according to latest results from the SEARCH for Diabetes in Youth study presented recently at the ADA 2020 Scientific Sessions.

Cross-sectional data from 1,095 young people with type 1 diabetes (T1D) and 285 with youth-onset type 2 diabetes (T2D) appear to confirm observations in adults that diabetes is associated with poor performance on tests of cognitive function.

Dr Allison Shapiro from the Colorado School of Public Health told the meeting the participants were those seen at a second follow-up visit between 2016 and 2019, with a mean age of 21.6 years and a mean diabetes duration of 11 years.

The study used the NIH Toolbox Cognition Battery to assess ‘fluid’ cognitive skills such as reasoning, processing speed and the ability to solve problems in novel situations, as well as ‘crystallised’ cognitive skills such as language and vocabulary.

It found fluid cognition in young people with type 2 diabetes was consistently and significantly lower than in young people with type 1 diabetes on a composite score (84.7 v 95.5) and across all subscores of processing speed, inhibitory control and attention, working memory and episodic memory.

As well, all scores in the group with type 2 diabetes and most scores in the group with type 1 diabetes were below the normative score of 100.

Dr Shapiro noted that fluid cognitive function is dynamic and sensitive to neurological changes that may occur in disease processes such as diabetes.

“Crystallised cognition skills have been considered a marker of premorbid cognitive function because skills such as vocabulary and language are thought to be stable and not influenced by neurological changes brought on by disease processes,” she said

The study found crystallised cognition scores followed the same pattern – lower in young adults with type 2 diabetes than in their peers with type 1 diabetes and lower than the normative population.

“In summary, youth and young adults with youth-onset T1D and T2D are performing below average on tests of fluid cognition.”

“This is important because deficits in cognitive function can negatively impact diabetes self-care, thereby potentially increasing the risk of diabetes-related complications.”

Dr Shapiro said the observed deficits in crystallised cognitive function could also impact medical literacy, which would further compound issues of self-care.

Professor Fergus Cameron, director of endocrinology at the Royal Children’s Hospital Melbourne, told the limbic there is increasing interest in the impact of dysglycaemia on the brain.

Ongoing research he has been involved with comparing children with diabetes with age, socioeconomic status and IQ matched controls has shown neurocognitive differences emerge over time.

“The short answer is that on average they lose about 0.3 of a standard deviation (SD) on full scale IQ score, about 30% have a DSM IV mental health issue, about 30% of them fail to transition to adult health care successfully, and they lose brain volume by about 0.3 SD in MRI,” he said.

“The more fundamental issue is how does it affect them functionally? Does it render someone unemployable – and of course it doesn’t. Will it show up in a basic school test? No.”

“What’s really interesting is that it has been shown that these changes in executive function impact on adherence, so you get this perpetuating cycle.”

Professor Cameron said it was an intriguing, multidimensional problem with impacts over the arc of a life from pregnancies exposed to gestational diabetes through to adulthood when micro- and macrovascular change associated with diabetes added to the complexity.

“The solution firstly is to try and reduce the incidence of DKA at diagnosis and then figure out this hierarchy of risk which may alter the priorities of care at different ages.”

“For example, if severe hypoglycaemia before the age of five is a key risk factor, then you’d want to avoid that and you might compromise a bit on other outcomes.”

“Or if for example glycaemic variability is a big issue, that might be an argument for insulin pumps,” he said.

Read more in a recent review article by Professor Cameron and colleagues.

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