The power of a good night’s sleep: Proper rest potential remedy for insulin management and cognitive decline

10 Jul 2023 --- Deep-sleep brain waves might control blood sugar and insulin resistance as non-rapid eye movement sleep improves the next-day peripheral glucose control, according to US-based researchers. Meanwhile, a study in the UK found that physical activity may not protect from cognitive decline if sleep duration is less than six hours per night. 

The US study, published in Cell Reports Medicine, investigated why poor sleeping increases the risk of developing diabetes. Brainwaves in a deep sleep at night are better at regulating insulin sensitivity, which improves blood sugar control the next day.

The study’s authors say that sleep can now be used as a non-invasive treatment for those with high blood sugar and Type 2 diabetes as it is a modifiable lifestyle factor.

“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,” says Matthew Walker, a UC Berkeley professor of neuroscience and psychology and senior 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 consequently and beneficially lowers blood glucose levels.”

Entering deep sleep switches the nervous system into calmness and low stress. Brain waves
Building on previous studies, the researchers reveal the role of combined brainwaves in humans’ critical bodily function of blood sugar management. Years of studies have examined eye movement during sleep and how slow brain waves respond to learning and memory functions. 

The same researchers previously studied how deep-sleep brain waves improved the brain’s ability to retain information and found that deep sleep improved the hippocampus’s ability.

While studying the brain waves of 600 participants and then the experiment was replicated to 1,900 individuals, the scientists found how deep-sleep improved glucose control the next day. 

The results were evident after removing other factors such as duration and quality of sleep, age and gender.

The study found a set of steps explanatory to why and how the brain waves during deep sleep relate to controlling blood sugar. They discovered that entering deep sleep switches the nervous system into calmness and low stress. 

Insulin regulation
While entering this state, there was a shown increased sensitivity of the glucose-regulating hormone insulin that instructs cells to absorb glucose from the blood, preventing blood sugar spikes.

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

“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,” says Vyoma D. Shah, researcher at Walker’s Center for Human Sleep Science and co-author of the study. 

Shah further notes the results adding to the therapeutic relevance of this discovery as the findings suggest a novel, non-invasive tool – deep-sleep brain waves – for mapping and predicting someone’s blood sugar control.

Sleep and cognition
The UK-based study, published in the Lancet Healthy Longevity, found that cognitive benefits gained from physical activity are not beneficial if sleep duration is low. The decade-long study included 8,958 respondents aged 50 to 95 at the start of the experiment.

Independently, both physical activity and sleep duration levels worsened cognitive performance and short sleep showed a quicker cognitive decline. 

“Our study suggests that sufficient sleep may be required to get the full cognitive benefits of physical activity. It shows how important it is to consider sleep and physical activity together when thinking about cognitive health,” says Dr. Mikaela Bloomberg, lead author of the study and research fellow at the University College London (UCL), UK, Institute of Epidemiology & Health Care.

“Previous studies examining how sleep and physical activity might combine to affect cognitive function have primarily been cross-sectional – only focusing on a snapshot in time – and we were surprised that regular physical activity may not always be sufficient to counter the long-term effects of lack of sleep on cognitive health,” Bloomberg adds.

The study confirmed prior research results that regular physical activity and sleeping six to eight hours per night are linked to better cognitive function. 

Variations throughout lifeFor participants over 70, cognitive benefits could be maintained even though sleeping for less than six hours. 
No matter how long the participants slept when the study started, those who were more physically active had better cognitive function. After ten years, the researchers found a quicker cognitive decline for those being physically active but sleeping less than six hours for those aged between 50 and 60.

However, for the older participants – 70 years old and above – the cognitive benefits could be maintained even though sleeping for less than six hours. 

“It is important to identify the factors that can protect cognitive function in middle and later life as they can serve to prolong our cognitively healthy years and, for some people, delay a dementia diagnosis,” says Andrew Steptoe, co-author of the study and professor at the UCL Institute of Epidemiology & Health Care.

“The World Health Organisation already identifies physical activity as a way to maintain cognitive function, but interventions should also consider sleep habits to maximize long-term benefits for cognitive health.”

The research team says the next step is replicating the study, examining a more diverse population and further investigating cognitive and sleeping domains.

The scientists excluded participants with self-reported dementia and those who showed indication of cognitive impairment, such as preclinical Alzheimer’s disease, did not affect the test results. 

Recently, botanicals have received attention for improved sleep quality. Kerry unveiled a blend of ingredients for improved sleep quality with ashwagandha. A study published earlier this year found that Hibiscus Syracuse L. flower enhances sleep quality. 

By Beatrice Wihlander