Sleep has critical roles in health and regeneration, and one of those is clearing the brain of metabolic waste, according to researchers from the US and Denmark.
Now, as reported in the journal Nature Communications, they’ve discovered in mice that the time of day matters, suggesting the process is controlled by circadian rhythms.
“Our group has shown that just being awake or asleep drastically changes how well the brain can clear waste,” says lead author Lauren Hablitz from the University of Rochester Medical Centre.
“When you’re asleep, cerebrospinal fluid [CSF] can enter the brain and more waste is cleared. Sleep ‘cleans’ the brain.”
We are most likely to sleep when we’ve been awake for a long time or when it’s night-time and our circadian clock kicks in.
“For the general population, this suggests that it isn’t simply being asleep that matters,” says Hablitz, “but when you sleep. Think about napping – normally not as effective as regular sleep. This may be why.”
To extend their findings, the team aims to investigate impacts of things that disrupt circadian rhythms in the real world, such as altered light and sleep.
“Chronic sleep disruption and shift work are associated with neurodegeneration and increased risk of getting sick,” says Hablitz, “and these observations could be because the brain’s waste removal system and brain/immune crosstalk is not timed correctly.”