You’re being brainwashed — and it’s good for you!
Danish scientists say they have gleaned new insight into our glymphatic system, which flushes out toxic buildup in the brain while we sleep.
This process is essential for healthy brain function and the possible prevention of disorders like Alzheimer’s disease — and it can be disrupted by at least one popular sleep aid, a new study found.
The glymphatic system is akin to “turning on the dishwasher before you go to bed and waking up with a clean brain,” said senior study author Maiken Nedergaard, of the University of Rochester and University of Copenhagen. “We’re essentially asking what drives this process and trying to define restorative sleep based on glymphatic clearance.”
Nedergaard and her team examined mice to see what happens inside their brain as they snooze. They found that their brainstem releases tiny waves of the molecule norepinephrine about once every 50 seconds during deep sleep.
Norepinephrine plays a key role in our “fight-or-flight” response by triggering the narrowing of blood vessels, which increases blood pressure and readies the body to react to stressful situations.
The rhythmic expansion and contraction of the blood vessels also propels surrounding fluid to carry waste away from the brain.
“You can view norepinephrine as this conductor of an orchestra,” said lead study author Natalie Hauglund, of the University of Copenhagen and the University of Oxford in the UK. “There’s a harmony in the constriction and dilation of the arteries, which then drives the cerebrospinal fluid through the brain to remove the waste products.”
Once Hauglund and Nedergaard confirmed that norepinephrine drives brain cleaning, they wanted to see if a sleep aid affects this process.
They gave mice the insomnia medication zolpidem, sold under the brand name Ambien.
Though the zolpidem-treated mice fell asleep faster, they had half as much norepinephrine wave activity during deep sleep and 30% less fluid transport into the brain than naturally sleeping mice.
The results suggest that the sedative may disrupt the brain-clearance system during sleep.
“More and more people are using sleep medication, and it’s really important to know if that’s healthy sleep,” Hauglund said. “If people aren’t getting the full benefits of sleep, they should be aware of that so they can make informed decisions.”
Hauglund said the findings, published Wednesday in the Cell Press journal Cell, likely apply to humans but require further testing.
