The science behind sleep has fascinated humans for centuries. While even the earliest Greek philosophers and scientists explored sleep, it wasn’t until the mid-20th century that the mechanisms of sleep started to take shape. Today, science on the benefits of sleep abounds. Everyone knows that a good night’s sleep is a key ingredient of a healthy lifestyle, boasting benefits to our hearts, weight, and minds. But much still remains to be studied to fully understand the links between sleep, our bodies, and our brains. Today, researchers continue to delve deep to understand how rest plays a role in our overall health.
Enter new work coming out of the Marche Polytechnic University in Italy. Under the guidance of neuroscientist Michele Bellesi, a team of researchers have spent time examining the brain’s response to poor sleeping habits. Using mice as the subjects for the study of how mammals’ brains respond to sleep or lack of sleep, the team found striking differences between well-rested and sleepless mice.
The scientists structured their study like this: they grouped the mice into four categories. One group was left to sleep for 6 to 8 hours (labeled “well-rested”); another was periodically woken up from sleep (labeled “spontaneously awake”); the third group was kept awake for an extra 8 hours (labeled “sleep-deprived”); and the final group was kept awake for five days straight (labeled “chronically sleep-deprived”). Then they collected brain scan images from the mice in each of the four groups.
What did researchers discover? In science terms, they found that during sleep, the mice’s brains actually changed states to clear away toxic byproducts of neural activity left behind during the day. For the chronically sleep-deprived, that same process occurred, but on hyper-drive. Scientists discovered that chronic poor sleep caused the brain to clear a significant amount of neurons and synaptic connections. (Remember that neuron and synaptic connections are the backbone of how our brains store and process information.) What’s more is that recovering sleep may not reverse all the damage.
Let’s break this down into layman’s terms. Sure, humans are not mice, but we are both members of the mammal family and share many traits. So scientists drew a corollary from their research, positing that as we sleep, our brain, in essence, eats itself. Not to worry, this is normal. But if we are consistently sleep-deprived, it overeats, and the results could be harmful to our daily brain function. And making up for today’s lost sleep tomorrow may not be enough to undo the harm.
Getting back to the science, Michele Bellesi recently explained the findings. “We show for the first time that portions of synapses are literally eaten by astrocytes because of sleep loss,” said the research leader. But Bellesi was quick to reassure us that this is not in itself a negative thing. Most of the synapses affected were larger and older. According to Bellesi, “They are like old pieces of furniture, and so probably need more attention and cleaning.”
Scientists have known that this process occurs every time we sleep. The purpose of astrocytes – a type of cell in the brain that cleans out worn-out cells and debris – is to refresh and reshape our brain’s wiring each day, to keep us in tip-top mental shape.
But this new research indicates that the process can ramp up to dangerous levels when we lose sleep. So rather than providing the benefits of refreshing the brain, in sleep-deprived subjects, the astrocytes kicked into high gear and actually started to harm the brain.
Perhaps the most troubling finding coming out of this research deals with the activity of microglial cells. These cells are responsible for the phagocytosis process, which means “to devour” in Greek. In essence, microglial cells are behind the process of our brains eating themselves.
Researchers found that microglial phagocytosis had also ramped up in the chronically sleep-deprived group. And this is a serious concern. We worry about this elevated response because unbridled microglial activity has been linked to neurodegeneration – meaning brain diseases like Alzheimer’s disease.
Still, many questions remain, like if this process is truly replicated in our human brains, and whether catching up on lost sleep effectively reverses any damage. But if we consider the fact that deaths attributed to Alzheimer’s disease have increased by a sharp 50 percent since 1999, this is serious business. Couple this point with together how hard it is for many of us to get a good night’s sleep, and the risks become even more clear.
While science still has a ways to go to fully explain the impact of these new findings in our daily lives, let’s hope they get there, fast. In the meantime, it’s our job to take care of our bodies by living healthily as best we can. No matter what future findings show, catching some restorative Z’s now is a great start to boosting our overall health, brain and body included.