BrainStuff Classics: Why Do We Sleep?

We spend somewhere around a third of our lives sleeping, but why? Learn what happens when you sleep (and what happens when you don't) in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,
I'm Lauren volke Bam and our former host Christian Sager,
has another classic episode for you today. The topic is
one that plagues me every time I'm on deadline or
wanting to finish one more chapter. Why do we sleep? Anyway? Hey,

(00:25):
I'm Christian Sager and this is brain Stuff. Here's a
quote for you from American light bulb man Thomas Edison.
He said sleep is a criminal waste of time inherited
from our cave days. Well, like Edison, we hear a
brain Stuff hate sleep. That's why we wanted to do
this episode to figure out why we have to do it.

(00:45):
Normal people spend thirty of their lives asleep, and most
are either like us and wish that they didn't have
to sleep so they could get more done, or they
just want to get a RESTful, uninterrupted night without waking up.
Studies actually show that six percent of adults claim to
have problems sleeping at least a few nights a week.
And here's the thing. Everyone's got to sleep. Yet we

(01:07):
still don't know exactly why, but we're going to try
to do our best to crack that case. Today that's right.
Let's review some theories for why we sleep, what happens
when we sleep, and what happens when we don't. Even
though we don't know why we sleep, there's all kinds
of educated speculation. The most prevalent is that sleep gives

(01:28):
our brain a chance to organize and process information, possibly
through dreams. Basically, our brain takes all the sensory stimuli
we received while we're awake and decides what to keep
in where to file it. Everything else gets trashed. It's
even possible that our ability to learn tasks actually benefits
from quote sleeping on it as a process is better

(01:50):
understood after our brain reviews and catalogs it. While most
agree with this memory consolidation theory, it's tough to pin
down since we all sleep oh differently. And here's another theory.
Sleep gives our bodies time to rest and repair. Or
how about sleep lowers our energy consumption so we conserve

(02:10):
the meals we eat. Other theories delve into the biochemical
mechanism of the brain. In a series of experiments on mice,
showed that cerebral spinal fluid was pumped around their brains
while they slept, expelling waste like molecular detritus and toxic
proteins into their livers for breaking down. So do we

(02:32):
sleep just to flush the toilet on our cerebral commodes? Well,
other sleep researchers were skeptical of the study that I
just mentioned, pointing out that there are some big differences
between a mouse's brain and humans. So while the answer
to why we sleep isn't written in stone, we all
know that when we sleep, both our mind and our
body feel refreshed. We at least know what's happening when

(02:54):
we sleep, right Well, most of us need between seven
to nine hours of sleep at night, but that changes
during different periods of life. For example, a newborn baby
might sleep twenty hours a day, but by the time
they're three months old, they recognize the circadian rhythm of
sleeping at night and waking up in the morning. And
when you're older, like senior citizen older, you can probably

(03:16):
get by on only six or seven hours a night.
Regardless of how long you're asleep, you must experience both
R E M and non R e M stages to sleep. Well.
That's rapid eye movement, not the band R E M.
From Athens, Georgia, A normal person spends of their sleep
in R E M, with each session lasting between five

(03:38):
and thirty minutes, and during this time our brain speeds up,
our eyes and face might twitch in R e M
because we're dreaming. We need around ninety minutes to fulfill
a complete cycle of R e M N non r
EM sleep, and researchers think this cycle ties sleep back
to our ability to process tasks and memories. Recording show

(04:00):
that many of the same neurons that fire when we're
learning are reactivated during our E M, consolidating the patterns
into permanently wired connections. But don't sleep too much more
than eight hours can lead to depression or even Parkinson's
and heart disease. Of course, if we don't sleep, that's

(04:20):
a whole other mess of problems. Rats will actually drop
dead if they go more than three weeks without sleep.
Us humans, we get lethargic, cranky, and foggy headed at first,
almost like we're intoxicated. We might even nod off into
micro sleep for a few seconds, and this is what
happens after one or two nights without sleep. By day three,

(04:41):
we start hallucinating and lose the ability to recognize reality
and that's if you're really pushing the boundaries of sleep.
Simply failing to get enough sleep is connected to obesity,
high blood pressure, a weakened immune system, heart disease, cancer,
and diabetes. And it's no big re elation that lots
of us don't get enough sleep. We might try to

(05:04):
get by on caffeine or nicotine, and alcohol is a
good sedative, but it doesn't actually provide the sleep we
need for neural processing. So, in the words of the
immortal poet Chris Ludicrous bridges, if you're tired, be quiet
and go to sleep. Today's episode was written by Ben

(05:25):
Bolan and produced by Tyler Clang. To hear more from Ben,
tune into his podcast Prediculous History, which is what it
says on the tip, but in a really fun way.
And of course, for more on this and lots of
other answers to annoyingly persistent questions, visit our home planet,
how Stuff Works dot com.