"Oxygen therapy could be used to enhance slow-wave states during sleep to ensure that individuals who may have disrupted sleep are getting enough of the restorative, slow-wave sleep," said Dickson. "Of course, this has to be tested first before this could become a therapeutic reality.”
Exposure to high levels of oxygen encourages the brain to remain in deep, restorative sleep, according to the findings of a new study carried out by University of Alberta neuroscientists.
If you’ve ever found yourself tossing and turning at night you may have reminded yourself from time to time to stop and take a deep breath. Just like when you feel you're approaching a panicked or anxious state throughout the day, being aware of your breath and increasing oxygen flow can immediately lead you toward a more relaxed state. Now, thanks to this new research, scientists are helping us understand how oxygen can help us maintain that state even while we’re asleep. They accomplished this by administering higher than normal levels of oxygen to animals while monitoring their brain activity.
"We found that when we administer oxygen, our subjects' brains switch out of active sleep, and remain in a deactivated, slow-wave state the entire time," explained Brandon Hauer, Ph.D. student in the neuroscience graduate program administered by the cross-faculty Neuroscience and Mental Health Institute. "Interestingly, when we removed the oxygen, the brain started cycling back through active, or rapid-eye-movement, sleep again.”
We have different stages of sleep that we cycle through throughout the night — rapid eye movement (REM) and non-rapid eye movement (NREM) — in four distinct stages. NREM makes up the first three stages of sleep, with each getting progressively deeper. The third stage, N3, is the deepest of the three and often referred to as “slow wave” sleep. The brain is now less responsive to outside stimuli and we are most difficult to wake up at this point. Heart rate and breathing both slow down, blood pressure falls, and even muscle activity slows. Although many associate REM sleep as the most important, it is actually slow wave sleep that revitalizes our body the most and leaves us feeling refreshed when we wake up the next day. During REM, our heart rate starts to pick back up during vivid dreams and our body is put back to work, essentially starting the cycle all over again.
Everything from our body positioning (lying on our back or lying on our side) to what we do or don’t eat before bed can impact how effectively we move in and out of these phases of sleep. Sleeping on your back, for example, significantly impacts the way you breathe throughout the night. The lower jaw can sink and change the shape of your air pathways. But maybe the most surprising thing about back sleeping is that it has been found to speed up brain aging. Research once found that rats who slept on their back cleared significantly less brain waste than rats that slept on their side. Specifically, amyloid beta, the protein fragment that’s a hallmark of Alzheimer’s Disease can be left in the brain, and this same effect can take place in humans who sleep on their back as well. Is this perhaps impacted by the amount of oxygen we can consume sleeping in this position as well as our ability to reach and maximize slow wave sleep?
Studies show that slow-wave sleep is when the brain goes into recovery mode. The frequency of our brain waves slow down and get wider, being produced at a frequency of at least 10 times slower than the fastest brain waves. Cortisol is reduced (the stress hormone) and hormones like prolactin and growth hormone are produced, supporting the adaptive immune system, which in turn helps us fight infection.
Knowing all this about slow-wave sleep, it’s clear the more of it you can get the better. It is is the deepest and most restorative phase of sleep, also known as deactivated sleep because it does just that to the brain, allowing it to essentially shut off while we rest. It’s believed to be a very important phase for memory consolidation, sometimes referred to as "sleep-dependent memory processing.”
This seems to be the stage where metabolites are cleared from the brain, muscles grow, and proteins reform," said Hauer, who conducted the research under the supervision of Professor Clay Dickson in the Department of Psychology. "Slow-wave sleep seems to be especially suited to recovery for both the brain and body. Interestingly, we saw a rebound effect after the brain remained in REM sleep, in which the brain reverted to slow-wave sleep for a longer duration as if it missed out on the slow-wave sleep during the activated stage.”
The findings are believed to be a major step in the development and understanding of what’s known as oxygen therapy, in which oxygen is used as a medical treatment. It’s a significant discovery in that field because air is typically made up of about 21 percent oxygen by volume, while oxygen therapy allows doctors to increase this intake up to 100 percent. Currently, oxygen therapy is applied to many patients with sleep apnea, which can result in a range of symptoms: high blood pressure, cardiovascular diseases, problems snoring, weight gain, memory problems, headaches, impotence, depression and irritability, and of course, insomnia. And while people of any age or weight can develop disruptive sleep apnea, but the disorder is most common amongst people that are obese, over 40, men with a neck circumference greater than 17 inches and women whose neck circumference is greater than 16 inches, enlarged tonsils and/or adenoids, smokers, and people who drink alcohol, or use sedatives or tranquilizers.
"Oxygen therapy could be used to enhance slow-wave states during sleep to ensure that individuals who may have disrupted sleep are getting enough of the restorative, slow-wave sleep," said Dickson. "Of course, this has to be tested first before this could become a therapeutic reality.”
But even if you don’t suffer directly from insomnia or a lack of sleep in general, boosting the amount of slow-wave sleep you get has been found to have tremendous health benefits. For example, growth hormone secretion is highest during this very sleep phase helping facilitate tissue repair and muscle growth.