People With Type 1 Diabetes Have Impaired Brain Function Due To Blood Sugar Highs and Lows

Scientists at Washington State University and McLean Hospital in Massachusetts conducted a study that suggests that significant fluctuations in blood glucose levels associated with Type 1 diabetes could affect the brain’s capacity for rapid information processing. The study also shown that particular groups of people—older adults and those with specific medical issues, for example—are more negatively impacted by these changes than others.

The study, which was published in npj Digital Medicine, discovered that there was a significant correlation between slower and less accurate cognitive processing speed at very low and very high glucose levels, with the greatest effect observed at low glucose levels. Making decisions in hectic situations and performing daily duties such as driving and running machinery both require optimal cognitive processing speed, or the capacity to react to and process information rapidly.

“Our findings suggest that minimizing blood glucose extremes could help people with Type 1 diabetes to improve not just their health but their cognition as well,” said co-senior author Naomi Chaytor, a professor and chair in the WSU Elson S. Floyd College of Medicine. “And because diabetes is a cognitively demanding disease that requires hourly decisions on how much insulin to take based on various factors, this could also potentially prevent a situation where glucose lows and spikes send people into a spiral of worsening diabetes self-management.”

Although earlier research had linked low blood glucose to improved cognitive performance in a lab setting, the researchers claim their study is the first to examine how blood glucose fluctuations affect cognition in people with Type 1 diabetes as they go about their regular lives. 200 individuals were recruited at four major U.S. diabetes centers, and the research team used smartphone-based cognitive tests and digital sensors that measure glucose every few minutes to collect repeated data on glucose levels and cognitive performance. Participants in the 15-day trial underwent glucose monitoring every five minutes in addition to three daily cognition tests.

Researchers found that when glucose levels were much higher or lower than normal, cognitive processing speed was compromised. This relationship was established by comparing cognitive test performance to glucose levels recorded at the time of testing. Additionally, they examined the participants’ sustained attention, which measures their capacity to maintain concentrate on a task for a prolonged period of time. They discovered that glucose variations had no discernible effect on this ability.

“It’s possible that sustained attention is impacted by high or low glucose that persists over longer periods of time, even though it does not appear to be affected by the short-term, moment-to-moment fluctuations in glucose that we looked at in this study,” said Laura Germine, co-senior author and director of McLean Hospital’s Laboratory for Brain and Cognitive Health Technology.

By comparing the effects of glucose variations on cognition across people, the researchers were able to identify variables that may indicate who is more likely to experience severe consequences. They discovered that this was true for the elderly and individuals with specific medical disorders, such as diabetes-related kidney, nerve, and eye damage, weariness, and a higher chance of sleep apnea.

“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,” said first author Zoë Hawks, a research investigator at McLean Hospital.

One unexpected finding was that, although performance declined when glucose levels increased even further, participants’ peak cognitive performance was correlated with glucose levels that were marginally beyond their usual range.

“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,” Chaytor said, adding that it’s possible that the brain habituates itself to a glucose level that it is used to.

The next phase of the research, according to her, will be to determine whether the glucose level linked to peak performance drops into the normal range when the duration of time spent above it is shortened. This can be done by using automated diabetes management systems.

In the end, the researchers want to figure out how to support Type 1 diabetics in achieving optimal cognitive function. Considering the growing body of data suggesting individuals with Type 1 diabetes may be more susceptible to dementia and cognitive loss, there may be long-term health benefits as well.

The National Institute of Diabetes and Digestive and Kidney Diseases, a division of the National Institutes of Health, provided the majority of the study’s funding.