Deep Sleep Brain Waves Predict Blood Sugar Control

Researchers have long suspected that a lack of quality sleep increases a person’s chance of developing diabetes. The why, though, has remained a mystery. New research by a team of sleep experts at the University of California, Berkeley, brings us one step closer to an answer. The researchers discovered a probable mechanism in humans that explains how and why deep-sleep brain waves at night can modulate the body’s sensitivity to insulin, improving blood sugar control the following day.

“These synchronized brain waves act like a finger that flicks the first domino to start an associated chain reaction from the brain, down to the heart, and then out to alter the body’s regulation of blood sugar,” said Matthew Walker, a UC Berkeley professor of neuroscience and psychology and senior author of the new study. “In particular, the combination of two brain waves, called sleep spindles and slow waves, predict an increase in the body’s sensitivity to the hormone called insulin, which consequentially and beneficially lowers blood glucose levels.”

According to the researchers, this is an important breakthrough because sleep is a changeable lifestyle component that may now be employed as part of a therapeutic and painless adjunct treatment for those with high blood sugar or Type 2 diabetes.

Aside from the potential novel mechanistic pathway, scientists discovered another advantage.

“Beyond revealing a new mechanism, our results also show that these deep-sleep brain waves could be used as a sensitive marker of someone’s next-day blood sugar levels, more so than traditional sleep metrics,” said Vyoma D. Shah, a researcher at Walker’s Center for Human Sleep Science and co-author of the study. “Adding to the therapeutic relevance of this new discovery, the findings also suggest a novel, non-invasive tool—deep-sleep brain waves—for mapping and predicting someone’s blood sugar control.”

The findings of the researchers were published today in the journal Cell Reports Medicine.

Researchers have been studying how the combination of non-rapid eye movement sleep spindles and deep, slow brain waves corresponded to an altogether different function—learning and memory—for many years. Indeed, the same UC Berkeley study earlier discovered that deep-sleep brain waves boosted the hippocampus’s (the brain’s learning center) ability to retain knowledge.

This new study, however, expands on a mouse study from 2021 and reveals a novel and previously unknown significance for these coupled brain waves in humans when it comes to the important physical function of blood sugar regulation.

The UC Berkeley researchers first evaluated sleep data from 600 people. They discovered that this specific linked set of deep-sleep brain waves predicted next-day glucose control, even after controlling for age, gender, and sleep duration and quality.

“This particular coupling of deep-sleep brain waves was more predictive of glucose than an individual’s sleep duration or sleep efficiency,” said Raphael Vallat, a UC Berkeley postdoctoral fellow and co-author of the study. “That indicates there is something uniquely special about the electrophysiological quality and coordinated ballet of these brain oscillations during deep sleep.”

The scientists then set out to investigate the descending pathway that could explain the connection between these deep-sleep brain waves sending a signal down into the body, ultimately predicting blood glucose management.

The team’s findings suggest an ongoing series of stages that may help explain how and why these deep-sleep brain waves are associated with greater blood sugar control. First, they discovered that stronger and more frequent coupling of deep-sleep brain waves predicted a shift in the body’s nervous system state into the more quiescent and soothing parasympathetic nervous system. They used heart rate variability as a surrogate to quantify the change in the body and the move to this low-stress state.

The team then focused on the final step of blood sugar balance.

The researchers also discovered that this deep sleep switch to the calming branch of the nervous system predicted an increase in the body’s sensitivity to insulin, a glucose-regulating hormone that instructs cells to absorb glucose from the bloodstream, preventing a dangerous blood sugar spike.

This is especially crucial for persons seeking to avoid hyperglycemia and Type 2 diabetes.

“In the electrical static of sleep at night, there is a series of connected associations, such that deep-sleep brain waves telegraph a recalibration and calming of your nervous system the following day,” Walker said. “This rather marvelous associated soothing effect on your nervous system is then associated with a reboot of your body’s sensitivity to insulin, resulting in a more effective control of blood sugar the next day.”

The researchers then examined a separate set of 1,900 people and found the same results.

“Once we replicated the findings in a different cohort, I think we actually started to feel more confident in the results ourselves,” Walker said. “But I’ll wait for others to replicate it before I truly start believing, such is my British skepticism.”

According to the researchers, the finding is especially fascinating because of the potential clinical significance years down the road. Diabetes medications that are already on the market can be challenging for patients to follow. The same can be said for the suggested lifestyle adjustments, such as changing food habits and regular exercise.

Sleep, on the other hand, is a relatively benign experience for the majority of people.

While sleep will not be the sole panacea, the promise of new technologies that can safely alter brain waves during deep sleep, as discovered by this latest research, may help people better regulate their blood sugar. That, according to the research team, is cause for optimism.

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