The Wired’s Sara Harrison breaks down the results of a study by Dr. Laura Lewis on the importance of sleep (as if you needed another reminder). Lewis and her team at Boston University Lab have revealed how our body clears toxins out of our brains as we sleep.
The Study
The study aimed to test the role of non-REM (deep) sleep in removing toxins in the brain by examining sleep cycles that were as realistic as possible. Here’s how they did that:
- Late nights: to ensure the sleep cycles were as realistic as possible, subjects were instructed to stay up late the night before so that they could drift off easily at midnight, when the tests were run.
- Non-invasive: Participants had to lie down and fall asleep inside an MRI machine and were fitted with an EEG cap to measure the currents flowing through their brains. The test was as non-invasive as possible, even forgoing the use of injected dye commonly used for mapping out the body during MRIs.
- Isolating Metrics: the MRI measured the levels of oxygen and cerebrospinal fluid — the clear liquid found in the brain and spinal cord — in the brain. This was to better understand their relationship during sleep.
Harrison notes how Dr. Lewis sacrificed her own sleep for science to conduct the late night study, running tests until 3am before sleeping in the next day: “It’s this great irony of sleep research,” Lewis says. “You’re constrained by when people sleep.”
The Findings
Lewis found that during non-REM sleep (also known as deep sleep), the following took place:
- Neurons synchronize:These specialized cells that transmit impulses start to switch on and off at the same time.
- Blood flow decreases: When they switch off or “go quiet” they have less need for oxygen and as a result, blood flow to the brain decreases.
- CSF fills in: When this happens, cerebrospinal fluid rushes into the added space and washes over the brain in large slow waves.
The results builds off of a previous 2013 study led by neuroscientist Maiken Nedergaard that showed toxins like beta amyloid, a potential contributor to Alzheimer’s disease, was cleared out in mice during sleep. Suffice to say sleep is as important for humans as it is for mice. “[The paper is] telling you sleep is not just to relax,” says Nedergaard. “Sleep is actually a very distinct function.”
The Implications
Harrison notes that this study only focused on non-REM sleep in healthy young adults and not on other sleep cycles and in older people, which means more research is needed. Still, the findings might help improve treatment for conditions such as Alzheimer’s: where previous medications just focused on targeting certain molecules like beta amyloid, understanding the important role cerebrospinal fluid plays means a new path towards other treatments. For one, Nedergaard says, future treatments might emphasize increasing the amount of cerebrospinal fluid washing over the brain.
Where we’re going with this
Even if we don’t have Alzheimer’s, we can’t ignore the important relationship between sleep, healthy brain function and mental health, issues of which are exacerbated by sleep problems especially in those with pre-existing conditions. To add to that, workers in our creative industry are more susceptible to certain issues such as depression.
Even for those who don’t suffer from said issues, it’s unlikely we’ll hear the conclusive end of the debate on how much sleep is good for creativity, with some arguments broadly praising the benefits of less sleep and others suggesting it depends on the type of creative. For that reason, we’re not going to flat-out suggest you get more sleep than you need to feel good nor will we be penning an Analysis titled “Why You Don’t Actually Need to Sleep That Much” anytime soon.
Rather, we take this study as proof of the overall importance of a good night’s sleep, which now that we see how cerebrospinal fluid is involved, could be affectionately (and accurately) called our daily “brain shower.” Just like a real shower, the exact length varies by the individual and you take as long as you need to start/end your day feeling clean, refreshed and creative.
