The science of the glymphatic system is still evolving, but one thing is clear: sleep matters for brain health — and we’re only beginning to understand why.
Deborah Kan is an award-winning journalist and founder of Being Patient. In this “Thought of the Week” column each Friday, she highlights one of the key stories shaping the future of brain science.
Dear readers,
My daughter’s friend John came back from a European vacation last week and when I asked him how it was, he told me he’d been staying up all night, getting four hours of sleep or less, and partying a lot. John described whole days he could barely focus, barely function, days where he “simply existed.”
I asked if he’d ever heard of the glymphatic system. He said no.
So to my daughter’s embarrassment, I started to explain it to him, standing there in my kitchen. And as I did, I realized how common it is that a healthy young person can go 20 years without ever being told that his brain runs a cleaning cycle, and that the cycle mostly runs at night.
It really wasn’t until 2012 that scientists identified something they named the glymphatic system, a network of channels that runs alongside the brain’s blood vessels, a kind of biological plumbing. Often referred to as the “janitor of our brain,” its job is waste clearance. During the day, the brain generates metabolic byproducts the way any hard-working organ does. The glymphatic system is how the brain flushes them out, and the system is most active during sleep.
Earlier this year, my colleague Simon Spichak wrote about a company building a device that fits in the ear to try to measure glymphatic flow in living people. Simon’s article points out that the findings on glymphatic biology have almost all come from rats and mice. Tracking the system in humans is still genuinely hard. The idea that it might help clear the proteins linked to Alzheimer’s is a promising line of thinking but certainly not an established fact.
What I was explaining to John is when he skips sleep, he is skipping the shift when the brain does its housekeeping. He could feel the cost the next day without ever knowing there was a system behind that horrible sleep-deprived feeling — but he’s 20. Four hours of sleep in a foreign city is practically the point, and most people his age don’t understand how sleep can impact behavior.
I’m not staying up until dawn in European clubs. But I have noticed something about my own nights. When I don’t drink alcohol, I sleep through the night. When I do, even just one glass of wine, my sleep is interrupted. I had always filed that under a minor annoyance. If deep, unbroken sleep is when the brain runs its cleaning cycle, then the nights I fragment my own sleep are nights I am cutting that cycle short.
We don’t yet know how to measure any one person’s glymphatic flow, and we can’t tell you what a run of broken nights costs a single brain over a lifetime. But we do know that sleep plays a real role in brain health. Good sleep hygiene is increasingly seen as one of the few modifiable factors in brain health. And understanding how it all works in your 20s will hopefully change the meaning of an all-nighter.
With hope,
Deborah