Sleep accounts for one-quarter to one-third of the human lifespan. But what exactly happens when you sleep?
Far from a passive experience, every night, for hopefully 8 hours, your body and brain engage in a highly active process that repairs muscles, improves memory, flushes toxins, and regulates hormones.
And that’s just what we know so far.
The consensus among sleep researchers today is that we have just begun to scratch the surface of what happens in our brains when we sleep. But new findings in the last few years are starting to reveal the complexity and importance of sleep in a whole new light.
Clearing Toxins
Neurons take up and send out electric and chemical signals to other neurons. The brain alone has about 100 billion neurons. Our “grey matter” accounts for roughly 20 percent of the body’s total energy consumption. All of this activity and fuel-burning also means that the brain generates a lot of waste. Two varieties are particularly concerning: beta-amyloid peptides and tau proteins. These compounds have been found in higher concentrations in people exhibiting dementia symptoms. Measuring for those compounds has become part of the diagnostic protocol for Alzheimer’s.
Evidence has been mounting that part of the role of sleep is to clear out what we don’t need, like information we take in during the day that doesn’t need to be stored in long-term memory as well as these dangerous metabolic waste products.
Now, researchers from Boston University have discovered that these toxic byproducts are, in fact, flushed out in waves by cerebrospinal fluid (CSF) during the slow-wave sleep phase.
A new paper published in the journal Science detailed the discovery process of finally capturing fMRI images of waves of CSF entering the brain for its nightly bath. Researchers now think that this crucial process can only happen during sleep and is not possible during wakefulness. Without regular, nightly cleansing, the buildup of metabolic waste can “gunk up the works,” so to speak, and lead to more problems later on.
More Deep Sleep, Less Anxiety
Intuitively, we understand the connection between our moods and insufficient sleep. Without enough rest we feel foggy, slow, irritable, and less able to control our thoughts and actions.
New evidence is emerging that shows these associations are not just in our heads. Or rather, the complex linkages between sleep, mood, emotional regulation, and our brains, is entirely in our heads.
In a paper published in the journal Nature researchers demonstrated that sleep deprived study subjects were left with brains that were actually wired for heightened anxiety. High-quality, non-REM sleep — often called deep sleep — is the most effective at reducing anxiety levels the following day, researchers found. They also noted that a sleepless night can make you up to 30% more anxious the next day. Researchers believe that deep sleep restores the brain's prefrontal mechanism that regulates our emotions, lowering emotional and physiological reactivity and preventing the escalation of anxiety.
So, while we all know that balanced nutrition and exercise are key components of a healthy lifestyle, there are more reasons than ever to also prioritize good, restful sleep for truly optimal health.