Researchers have found that naturally occurring glucose fluctuations impact on brain function in people with type 1 diabetes.

The study also showed that some people were more prone to the effect of glucose fluctuations on cognitive function.

Another key finding was that brain function was slower during periods when glucose levels were significantly higher or lower than an individual’s normal level.

While prior studies have highlighted that cognitive working is impaired by very low and high glucose levels, investigating the impact of naturally occurring glucose fluctuations outside of a lab setting has proved to be more difficult.

This has prevented researchers from acquiring high-frequency measurements from the same person over a period of time. These measurements are vital in understanding if glucose fluctuations have the same effect on brain function for everyone.

Lead author of the latest study, Zoë Hawks, PhD and research investigator at McLean Hospital, said: “In trying to understand how diabetes impacts the brain, our research shows that it is important to consider not only how people are similar, but also how they differ.”

Advances in digital testing allowed researchers to collect data via digital glucose sensors and smartphone-based cognitive tests from 200 people with type 1 diabetes.

Glucose levels were recorded every five minutes while the cognitive data was measured three times a day for just over two weeks, as participants went about their normal life.

Researchers then took these data points and used machine learning to scope out whether the effect of glucose on cognition differed from one person to another.

They found that when glucose levels were significantly higher or lower than usual, cognitive processing speed was impaired but sustained attention was not.

The team theorised that short-term, moment-to-moment glucose fluctuations may impact on processing speed, while high or low glucose levels over longer periods of time could affect sustained attention.

The results showed that the impact of glucose fluctuations on cognitive speed differed from person to person. This impact was seen most in some groups of people, including older people and those with certain health conditions.

Co-senior author Laura Germine, PhD and director of McLean’s Laboratory for Brain and Cognitive Health Technology said: “Our results demonstrate that people can differ a lot from one another in how their brains are impacted by glucose. We found that minimising glucose fluctuations in daily life is important for optimising processing speed, and this is especially true for people who are older or have other diabetes-related health conditions.”

The researchers also made a surprising discovery – that participants’ peak cognitive performance ran parallel with slightly raised glucose levels.

Co-senior author Naomi Chaytor, PhD and professor and department chair in the Washington State University Elson S. Floyd College of Medicine, said: “This was an important finding because people with diabetes often report feeling better at a glucose level that is higher than what is considered healthy.

“It could be that your brain habituates to a glucose level that it is used to. So a next step in this research is to see whether the glucose level associated with peak performance shifts down into the normal range when the amount of time spent above range is reduced, which can be achieved through use of automated diabetes management systems.”

Read the study in npj Digital Medicine.

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