A new study has uncovered the mechanism by which the brain waves produced during deep sleep can predict blood glucose control. The discovery not only highlights the importance of sleep in managing diabetes but it also offers a novel way of mapping and predicting the disease.
Sleep quality has been linked to many diseases, including dementia and diabetes. Concerning diabetes, previous studies in humans and animals have found that insufficient sleep is a causal factor in impaired blood glucose regulation. In contrast, good sleep has been shown to improve glucose metabolism.
With a new study, researchers at the University of California, Berkeley are a step closer to understanding why sleep is so important to blood glucose control, and it has to do with brain wave patterns produced during deep sleep.
Sleep stages fall into two broad categories: rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. There are three stages to NREM sleep which you progress through, characterized by increasingly deeper sleep. Stage 3 NREM sleep, the deepest stage, makes up about 25% of total sleep time in adults and is what you need to wake up feeling rested.
During stage 3 NREM sleep, the brain produces mostly large delta waves and so-called slow oscillations, which may help synchronize delta waves and bursts of coherent neural activity known as sleep spindles. Prior research has shown that the coupling of slow oscillations and sleep spindles affects learning and memory, but it was the effect of coupling on blood glucose that the researchers focused on.
“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, corresponding author of the 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.”
After first examining sleep data from 647 people and their next-morning blood glucose and insulin measurements, the researchers found that the brain wave coupling predicted next-day blood glucose control, independent of factors such as age, gender, and sleep quality and duration.
“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, the study’s lead author. “That indicates there is something uniquely special about the electrophysiological quality and coordinated ballet of these brain oscillations during deep sleep.”
Looking deeper, the researchers uncovered a series of physiological steps that may explain how these deep-sleep brain waves led to better blood glucose control. They found that stronger, more frequent coupling of slow waves and spindles led to activation of the parasympathetic nervous system (PNS), the network of nerves that relaxes the body after periods of stress or danger, as demonstrated by a variable heart rate. They also found that activation of the PNS increased the body’s sensitivity to the glucose-regulating hormone insulin, leading the cells to absorb glucose from the bloodstream and preventing a spike in blood glucose.
“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,” said Walker. “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.”
Armed with this information, the researchers replicated their study on a larger sample of 1,900 people. Slow oscillation-spindle coupling during NREM sleep again predicted improved fasting blood glucose in the second cohort.
“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.”
Interestingly, while the study predicted the effect of deep-sleep waves on insulin sensitivity, the researchers found it did not affect pancreatic beta cells, the cells that secrete insulin.
The researchers point out that their findings don’t contradict or challenge the association between diabetes and sleep as a risk factor for the disease. Rather, they say, measuring deep-sleep wave coupling could be viewed as an additional way of providing insights into diabetes.
“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 Shah, a study co-author. “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.”
If nothing else, the study re-emphasizes the importance of getting a good night's sleep in managing diabetes.
The study was published in the journal Cell Reports Medicine.
Source: UC Berkeley
