By: Gregory Brown, MD/PhD Candidate
We all know sleep is important. If it wasn’t, why would, we do it 1/3 of our day. Sleep helps with mood, attention, and can regulate metabolism. But it could also be important in clearing trash from the brain, thereby preventing the onset of Alzheimer’s disease.
One of the key features of Alzheimer’s disease is the build up of a toxic metabolite (trash molecule) called amyloid-β (Aβ)
Sleep increases metabolite clearance from the brain
Scientists from the University of Rochester, Xie et al. wanted to understand how sleep was involved in metabolite clearance. Their findings indicated during sleep in mice that cerebrospinal fluid (CSF) could flow more easily in between cells and clear out waste. A possible reason could be due decrease adrenaline (the fight or flight hormone) activity.
In more scientific terms, sleep increases the interstitial space, decreasing resistance to CSF flow, which enables glymphatic clearance of neurotoxic metabolites, and this may be partially due to the decreased noradrenergic activity during sleep.
The authors also wanted to better understand the factors contributing to the increased CSH influx in the sleep state. They hypothesized that neuromodulators of the awake state, such as norepinephrine, could be inhibited to induce an artificial resting state, that would increase CSF influx. After injection of a norepinephrine receptor antagonist, the CSF trace area covered increased, albeit to levels about half of the sleep and awake levels. This is expected as the animal is not fully asleep, but instead resting, although the brain wave patterns did mimic sleeping mice.
These findings were replicated in anesthetized mice during normal wake hours (8-10p.m.), indicating the findings are not due circadian rhythms. An alternative explanation could be the findings are a gravity-based phenomenon: increased intake of CSF is due to the decreased force of gravity when the mouse places its head down to rest.
Clearance of toxic metabolites explains rested sleep
Anecdotally, people report feeling refreshed after sleep, but the mechanisms underlying the restorative mechanisms remain poorly understood. These experiments highlight that sleep may be important in removing waste from the brain. The clearance of toxic byproducts from the brain could provide reasoning for better cognitive functioning associated with sleep.
One benefit from chiropractic adjustments could also be an increase flow of CSF, which clears trash from the brain. Providing a clearer and more refreshed feeling.
There are numerous benefits to sleep, and the ability to clear toxic proteins that are known to be associated with Alzheimer’s disease is just another one. Make sure to get enough sleep to keep your brain functioning at tip-top shape.