For a long time, experts have believed that one of the reasons sleep is so important for our overall health is because our brains need time to reset and kind of clean house.

To get rid of the toxins that build up during our awake hours.

This recent study, though, suggests that might never have been the case at all.

Sleep is an absolute necessity for human beings, but the truth is that science don’t know a whole lot about the function itself.

That said, this study says “how metabolites and toxins are cleared from the brain is unresolved,” contradicting one of those most popular theories.

The team from Imperial College London found evidence in mice that glymphatic clearance was actually less efficient during sleep and under anesthesia.

In mice that were asleep, clearance was reduced by about 30%. If they were anesthetized, it was around 50%.

Co-lead Professor Nick Franks says that is very telling.

“The field has been so focused on the clearance idea as one of the key reasons why we sleep, that we were very surprised to observe the opposite in our results.”

Another hypothesis that they’re disputing is that impaired sleep and impaired waste removal could accelerate Alzheimer’s disease.

Now, author Bill Wisden believes a different underlying mechanism could be at work.

“It may well be that having good sleep does help to reduce dementia risk for reasons other than clearing toxins.”

While some researchers had been coming to similar conclusions on their own, others, like neuroscientist Maiken Nedergaard, still disagree.

“You can’t just come in and do something that’s completely different and say all the old data is wrong. I’m actually shocked that this paper was published.”

Nedergaard published the seminal study connecting sleep and Alzheimer’s disease back in 2013.

Detractors claim the new study’s method of injecting dye directly into the brain could have created unreliable data by damaging tissues and increasing intracranial pressure.

Nedergaard definitely agrees.

“They are unaware of so many basic flaws in the experimental setup that they have.”

She also raises the issue that the mice weren’t in natural sleep, that there’s no way to know for sure that the dye successfully reached the tissue, and that measurements of glymphatic drainage weren’t taken from optimal locations.

The team in question was as surprised by the results as anyone else, and are now excited to do more.

“The other side to our study is that we have shown that brain clearance is highly efficient during the waking state. In general, being awake, active and exercising may more efficiently clean the brain of toxins.”

This is a charged debate that is unlikely to be resolved anytime soon.

In the meantime, get more sleep.

It can’t hurt.

If you found that story interesting, learn more about why people often wake up around 3 AM and keep doing it for life.