The Science of Sleep

[Music] if you're anything like me you might still be cursing daylight savings time from a few weeks ago but why is it so hard to make your body wake up an hour earlier or adjust to an entirely different timezone it turns out that you're not just lazy your body has an internal clock that has its own plan in mind maybe you're a world traveler and you think nothing across and a half a dozen time zones in a couple hours maybe you work at night and it's finals week and sleep is less important than passing calculus or maybe you just co-hosted a 48 hour livestream with your brother hey it's your choice but if take it to the extreme living the night life can mess you up leaving you exhausted and confused and probably sick that's because you like most other inhabitants of the earth have a special biological system that keeps your body in sync with the cycles of day and night it's your circadian rhythm and unlike your alarm clock it doesn't have a snooze button our internal timekeeping device is logically enough synchronized to the rising and setting of the Sun many of your body's systems are calibrated to the appearance and disappearance of natural light and when we mess with that things can get out of whack in a hurry circadian comes from the latin cerca diem or approximately a day and pretty much all living organisms down to algae and bacteria have their own circadian rhythms whether you're an insect bird or a mammal those rhythms affect the three big necessities eating sleeping and mating everything from testosterone secretion to bowel movement suppression is controlled by this daily cycle in humans scientists are slowly beginning to understand how these natural oscillations take place every day what we're pretty sure about is that the main regulator is circadian rhythm can be found in the hypothalamus a small area at the base of your brain that's responsible for connecting the nervous system to your endocrine system our biological clock is dictated by a group of nerve cells within the hypothalamus called the suprachiasmatic nucleus or SCN this is connected to our optic nerves allowing the SCN cells to respond to light and dark so in the morning when our optic nerves sense like the Sen send signals to raise our temperature heart rate blood pressure and delay the release of hormones like melatonin that helps us with the sleeping researchers have found that as our body temperatures rise throughout the morning our memory alertness and concentration also sharpens so we tend to be at our cognitive best in the late morning and that is generally followed by an afternoon law in fact while our desire to sleep is strongest from 2 a.m. to 4 a.m. a close second is between 2 p.m. and 3 p.m. that may sound counterintuitive unless you have ever had a class at 2:00 p.m. in a nice warm room and suddenly that wooden desk starts to feel a lot like a featherbed this suggests that napping is an important and natural part of our daily rhythms so don't feel bad about it no other species exhibits the same once a day sleep pattern that most humans have become accustomed to and there's growing evidence that mid-afternoon napping might be in all of our best interests that afternoon Lola is followed by another period of alertness but in the evening as the Sun disappears the SCN again picks up those signals of changing light from our eyes organs shift into low gear our bodies temperature cools and sleep induced hormones are activated problem is that our daily schedules do not correlate with sunrise and sunset anymore but with working and studying in late night reading we're constantly fighting that master clock that's been trying to keep us in sync since we were babies scientists have linked disruptions to our natural rhythms to health issues ranging from diabetes and obesity to depression and dementia it's believed that up to 15% of our genes may be regulated by circadian rhythms so when you get off that next transatlantic flight or finished pulling that all night or do yourself a favor listen to your body and take some more naps I'm gonna go down for one right now cuz if we're approaching the 2:00 p.m. thing so I'm not sure how this is gonna look with the great screed you guys but I don't care I'm sleepy while Hank catches some quick Z's on the floor there I'd like to bring up a question that's been bothering me why do we even need sleep some animals like dolphins can just turn off half their brain at a time and people are known to pull all-nighters to squeeze in extra work or party time so how important is sleep to humans really even though the average person will spend 25 years of their life asleep there's no scientific consensus as to why exactly we do it one thing we know for sure our brains definitely think that sleep is important deep in your hypothalamus the tiny nut sized region at the base of your brain you have a little cluster of cells that acts like a timer called the suprachiasmatic nucleus when you're exposed to light this little cluster busily releases awake hormones like cortisol and suppresses the release of sleepy hormones like melatonin when it's dark it does the opposite a second trigger for sleep is believed to be the build-up of the compound adenosine in the brain adenosine is a byproduct of your neurons and other cells when they burn up adenosine triphosphate the main molecule that our bodies use to store energy research suggests that when a bunch of leftover adenosine accumulates in your brain you get sleepy we talked about adenosine before when we went into the science of caffeine because caffeine works by bonding to the same receptors as adenosine tricking the body into thinking it's not tired but when you do sleeve for those adenosine levels drop as it's gradually reabsorbed by your neurons this is partly what makes you feel rested when you wake up so we sleep when our brains tell us to sleep but that doesn't answer the larger question why are we wired to sleep it seems like a kind of terribly inconvenient thing to have to do also super dangerous if you're surrounded by Jaguars or something there are lots of theories out there and it's unlikely that any of them alone is the single answer instead they may all contribute to this weird urge that we have to lapse out of consciousness for starters all mammals and birds sleep and other critters like reptiles insects and fish exhibit some kind of sleep like behavior that even includes the millimeter long nematode worm which experiences stress when denied rest some scientists suggest that inactivity at night is an evolutionary adaptation that boosts an animal's survival rate by keeping it out of danger when it would be most vulnerable basically sleep could be a way to keep still so you would track less attention and yet lions sleep a whopping 15 hours a day well mr. giraffe arguably a tasty meal for said lion gets less than two hours a day so another theory is that sleeping might be a way to conserve energy much of life at least in the wild is about procuring calories to keep going so going dormant for about thirty-year day could be a smart move humans use about ten percent less energy when they're sleeping as our breathing and heart rate and body temperature all take a dip but the broader support out there for sleep theories is that it provides restoration sleep after all is when you grow muscle tissue your cells synthesize proteins your tissues repair themselves and growth hormones are released but surely we can take care of that without having to be unconscious right like why can't our cells fix themselves while we're sitting on the couch watching Real Housewives of Milwaukee because our brains need sleep as much as our bodies do emerging research suggests that sleep allows the brain to breed Juvonen maybe more importantly reorganize this theory is known as brain plasticity we all do and see a lot of different stuff every day and we'd probably like to remember most but not necessarily all of it when we wake up brain plasticity theorizes that sleep is when our brains replay and store the events of the day providing eight hours or so for the processing and consolidating of new memories this theory has been supported by tests on human subjects and one experiment a set of volunteers memorized sequences of patterns in the morning while the second set memorized them in the evening the morning group had their memories tested 12 hours later without sleeping and the evening group was tested 12 hours later - but after they'd slept and the evening group proved better at recalling the patterns it may actually be good advice to take a nap while you're stuck on your problems or sleep on a big decision that you have to make your brain may need that time to process everything you've observed but if sleep helps reinforce memories what about the stuff we like to forget like I don't have any reason to remember the color the car that cut me off this morning or the words to the radio commercial where the guy's singing about furniture luckily sleep can help clear out all that excess junk from our brains when you form memories during the day your brain strengthens the synapses or junctions between neurons learning new things often causes neurons to create entirely new synapses by tracking the bursts of electrical activity that happened a thousand times each night among your billions of neurons scientists have discovered that during sleep both high frequency and low frequency bursts increase but moderate frequency bursts decrease in other words your brain is choosing to either rev up or calm down the firing between each of those synapses you made while you were awake ultimately strengthening or weakening each connection so those a little sad when you think about it when you wake up the insignificant details about the previous day are prob I lost forever but keep in mind that without this daily cleaning your brain would face a major energy shortage and space crunch in a way this function of sleep is kind of like defragging a harddrive problem is people Americans in particular don't get enough sleep and a survey conducted at the National Sleep Foundation Americans on average get over an hour less than the recommended eight hours and night and teenagers need even more in addition nearly 20% of Americans report problems sleeping more than 200-thousand car accidents each year caused by sleepy drivers killing more people than drunk driving it doesn't take long for the brain and body to feel the effect of sleep deprivation and the problems compound with time just go one night without sleep and your brain quickly starts trying to scramble beginning with the amygdala the part of the brain that tells the body to be prepared for danger short-term sleep deprivation throws the amygdala into overdrive which in turn shuts down the prefrontal cortex that's the part of the brain that controls logical reasoning among other things so a single all-nighter can put you in a state that one researcher is called emotional jello because when it bypasses the prefrontal cortex the sleep-deprived brain connects instead to another part that evolutionarily speaking is one of the oldest and most primitive regions it's called the locus coeruleus or the blue spot of your brain because for some reason the tissue is actually blue its job is to make you respond instinctively to stress and panic only it can interpret pretty much anything as a threat a swerving car a terse email an offhand remark by a boyfriend leaving you anxious and suspicious of everyone and everything and the longer you go without sleep the worse things get memory and speed control are the next to suffer but after several days things really start to get weird general paranoia can give way to increasingly vivid hallucinations some theorize that this is your brain actually forcing you into a waking sleep but the question is can a lack of sleep actually kill you and the answer is almost definitely yes sleep is closely tied to immune health studies have shown a 50% decrease in antibodies and test subjects who were only moderately sleep deprived for one week exposing them to a host of illnesses and in a famous sleep study from the 1980s conducted by sleep researcher Alan rexif in a group of rats deprived of sleep all died within two weeks the cause as far as rec shift could tell was simply exhaustion nothing physically was wrong with them a follow-up experiment conducted in 2002 similarly failed to find an unambiguous cause of death so probably you want to know how long can you possibly go without sleep well the longest documented case of a person voluntarily staying awake is 264 hours or roughly 11 days it happened in 1965 when 17 year old Randy Gardner set the record as part of his science fair project Gardner emerged relatively unscathed physically most likely a result of his age but he was described as being cognitively dysfunctional at the end while awake he experienced blurred vision and involuntary eye movements and his hallucinations included seeing fog around street lights feeling a band of an imaginary hat and believing that he was a running back for the San Diego Chargers so lesson here I think is don't tried to beat Randy Gardner's record at your next school science fair there's really nothing good that can come of it okay so sleep isn't going away anytime soon feel free to take that post feast nap now or after this episode but sometimes falling asleep is easier than it sounds if it's so important why can it feel almost impossible as many as 60 million Americans suffer from insomnia so it's not much of a surprise that when Google sent us their list of most asked questions in the english-speaking world how can I fall asleep was pretty close to the top 60 million people that's weird since you know it's literally impossible not to sleep and if you're one of those people who's up in the middle of the night googling sleep solutions it might help you to learn a little about the science of sleepers thing you should know if you're having a hard time getting some shut-eye is that you're wired to sleep regular hours going to bed the same time each night and waking up the same time each morning having a regular wake up time seems to correlate pretty highly with the ability to fall asleep consistently this is because it keeps you aligned with what's known as your circadian rhythm your body's natural tendency to stay in sync with the cycles of day and night and you know what controls your body's circadian rhythm more than anything else light a lot of the help you get falling asleep comes from hormones they lower your heart rate and reduce your blood pressure and basically let you relax the key player here is the hormone melatonin and it's regulated by your exposure to light in darkness it flows freely but when you're exposed to light whether natural or artificial the release of melatonin stops so you know what that means no phones or laptops in bed the light emitted by electronics confuses your body into not knowing that it's time to sleep so scientists suggest at least an hour of screen free time before bed though I am completely incapable of that myself another obvious enemy of sleep caffeine even though you might think that cup of coffee after dinner might only affect you for an hour or so studies have shown that caffeine consumption as much as 12 hours before bedtime is linked with insomnia and even the way you think about sleep can affect your sleep patterns worrying about not getting enough sleep is a common enough cause of insomnia that has its own name sleep onset insomnia but you know what's really weird a lot of the time when we feel like we can't sleep we actually are sleeping when scientists rouse patients in the first or second stages of sleep more than 60 percent of them say that they weren't sleeping even though they were now of course there's a whole class of medications that will help you sleep from antihistamines to pharmaceuticals known as hypnotics which include ambien and lunesta but research has shown that while patients can fall asleep faster on hypnotics the effect is small adding only about 15 minutes to their sleep times other studies indicate that our minds are significantly more powerful than any medications in double-blind studies patients who were simply told that they were taking a sleep drug ended up sleeping far better than patients who were told they weren't so if you want to know how to sleep the answer is right there in your head now as part of our work answering the world's most asked questions we asked you our scishow viewers a few questions and one was how many hours per night you sleep and it's bad news only 10% of you are sleeping more than eight hours per night and eight and a half is the doctor recommended amount and over half of you report having trouble getting to sleep at least once per week and now it's time for meaningless correlations the best sleepers for countries where we had enough data to make any sort of judgment were Saudi Arabians with 76% reporting that they experienced insomnia infrequently or never most of Europe scored better than average with the Netherlands Russia and Spain all sleeping relatively soundly the English speakers in the US UK and Australia all had some of the worst scores and finally unsurprisingly our staggeringly unscientific survey reports that people who commonly drink coffee soda energy drinks or tea are all more likely to suffer from insomnia oh right don't look at your screens before bed that's doable sometimes though sleep problems aren't all in our heads or entirely in our hands insomnia is complicated and it's not the only thing that can go wrong while you slumber say you've been napping like between classes or after a long night out or I don't know after broadcasting on YouTube for 48 straight hours to raise money for charity now imagine you're waking up and suddenly you discover that you can't move you want to speak but you can't your mind is acutely aware of what's happening but you were powerless to get your body to do anything it may last a few seconds it may last a few minutes in rare cases it can last more than an hour it's called sleep paralysis and you might not have to imagine it because up to 40% of us have experienced this sleep disorder at some point in our lives I am one of them we don't like to think about the bad things that can go on while we're in dreamland just as we hate the disorders that keep us from even falling asleep hello insomnia but even though we've talked a lot on this show about the science of sleep why we need it why we dream and where dreams come from there is a whole other polymorphously messed up realm of human biology that explains what happens when sleep turns against us we can't turn our brains off we forget to breathe we have waking hallucinations some of us even walk eat run and have entire conversations when we're asleep the half-asleep brain is a crazy place and once you understand it you may never see the back of your eyelids the same way again when most people think of the things that cramp our sleep style they think insomnia but defining diagnosing and treating this most common sleep disorder can be tricky in fact for a long time most scientists considered insomnia to be a symptom of another problem like depression anxiety as much stress substance abuse a traumatic injury even jet lag though today insomnia is considered by many to be a chronic disease of its own that interacts with other medical conditions so if you've ever had prolonged trouble falling asleep or staying asleep but you don't have any other health issues then doctors would probably say that you have primary insomnia if you do have something else going on like a physical or psychological condition then you've got secondary insomnia and most cases of secondary insomnia are chronic meaning it lasts for more than a month there are also cases of acute or short-term insomnia which is usually triggered by stress or some specific life events whatever the cause scientists believe these Insomnia's are the result of the simple but eternal struggle between arousal and sleepiness Florin more research is suggesting that a condition known as hyper arousal where the nervous system remains in a constant state of alert maybe the main reason for chronic insomnia hyper arousal is basically a prolonged version of your body's fight or flight response you know that feeling your stress hormones ramping up your heart and respiration rates increase for most people this response disappears pretty quickly but for many insomniacs it can last all day into the night and that makes it difficult for the body to relax obviously but what's there to be afraid of once you have dozed off well sleep apnea is one of the more serious disorders simply put it's when you're breathing is interrupted while you're sleeping apnea comes from the Greek word for want of breath for some people it happens once or twice per night in serious cases it can happen more than a hundred times per hour though relatively common more than twelve million Americans have it the most severe forms of sleep apnea can lead to heart failure and stroke it's also been linked to diabetes one of the more troubling aspects of sleep apnea is that the victims don't always realize they have it the most common form obstructive sleep apnea happens when the muscles at the base of the tongue and the uvula that fleshy piece of tissue at the back of the throat collapse if this collapse blocks the airway only partially then you get snoring as air tries to squeeze through but apnea occurs when the airway is completely blocked when this happens blood oxygen levels drop fast which in turn tells the brain that breathing has stopped and that those muscles have to reopen the airway posthaste so this whole conversation between your body parts can last from a few seconds to a few minutes usually without the person ever waking up needless to say though this does not make for very restful sleep and there are all kinds of treatments for this kind of apnea but most people end up using a continuous positive airway pressure or CPAP machine it has a mask that fits over the mouth and nose and gently blows air into the throat helping to keep the airway open which doesn't sound very restful either another type of a disorder central sleep apnea is much more rare instead of a physical blockage in your throat that prevents breathing this is an interruption of the brain signals that tell the body to breathe until recently there were a few effective treatments but scientists are experimenting with a new pacemaker-like device that sends an electrical impulse to stimulate the diaphragm to breathe during sleep ok so forgetting to breathe is pretty bad but sleep disorders get downright dangerous when it comes to sleepwalking hardly because though it affects about 15% of people it is more common in children between the ages of 3 & 7 sleepwalking also known as somnambulism almost always occurs during the first third of the night that's the part of the sleep cycle we call non-rapid eye movement sleep and it's generally a period of deep sleep character by slow brainwaves while there's no consensus as to what causes this condition there are a few theories as to why people begin walking eating running even having conversations while the brain thinks it's asleep some scientists think it's caused by the brain trying to circumvent other stages of sleep and go directly from deep non REM sleep to full-on wakefulness others point to a chemical messenger in our body is known as gaba which normally serves to slow down activity in the brains motor system turns out that children lack the fully developed neurons that release GABA so without a full network of connections in the brain to keep motor activity under control it may be easier for young brains to instruct the body to move around while it's asleep which is crazy because have you seen how much children move around when they're awake sometimes the causes of sleepwalking are external and pretty controllable like sleep deprivation stress and drug use but scientists have also discovered that some people are genetically predisposed to it's a study conducted on families with at least four generations of sleep walkers have traced the condition to a defective section on chromosome 20 and a mother or father who carries this defect has a 50% chance of passing it on to their children but this is not the case with sleep paralysis which I experience sometimes it's a little weird sometimes even a little scary though I know it's temporary but why does this happen why does my brain in my body decide to freak me out first thing in the morning in some cases sleep paralysis is a symptom of narcolepsy a disorder that causes people to have an overwhelming need to sleep but it also regularly happens to non narcoleptics like me the weird feeling of being conscious but unable to move generally occurs as you're falling asleep but it can also strike you as you're waking up scientists believe that a main cause is entering REM sleep soon after lying down bypassing the stages of non REM sleep that normally happens first typically REM dominates the later stages of sleep which are also when the most vivid dreams occur during this deep sleep your muscles are essentially paralyzed most likely to prevent you from acting out whatever crazy space unicorn riding dream you're experiencing sleep paralysis occurs when you wake up in the middle of all of this and suddenly you're aware of the fact that moving is impossible recent studies have also found that the same neurotransmitters that affect sleepwalking may also cause sleep paralysis University of Toronto scientists discovered that both GABA and glycine switched off the brain cells that allow muscles to be active during REM sleep at least in lab rats now in the most severe cases of sleeper alysus victims also experienced frightening and bizarre hallucinations say could be visual or auditory and often involves shadows or hearing voices and footsteps are seeing images of humans and animal figures Asian Allah victims will also feel pressure on their chest and have trouble breathing scientists have described this phenomenon as a dreaming wild awake me I prefer to do my dreaming while asleep thank you very much and hopefully I didn't make you afraid to go to bed tonight okay Hank keeps talking about those 48-hour livestreams which seems like a tease if you want to join him this year project for awesome is starting Friday December 7th and you can totally sleep when you need to just not too much yep I did say too much because it turns out getting too much sleep is also bad for you when people talk about having too much of a good thing they usually mean over indulging in something like cake or fast food things you probably enjoy even if they aren't very good for you but what about something that's objectively important to your health and well-being like sleep well it turns out that you can get too much of that - most people need seven to nine hours of sleep and over sleeping is connected to health problems like depression heart disease and diabetes a 2014 study of eight hundred and ninety four pairs of twins for example showed that the genetic risk of depression was higher in subjects who got less than seven hours of sleep or nine or more hours of sleep every night meaning people who overslept or under slept were more likely to be depressed because of genetic factors as opposed to environmental ones and according to a study on the sleep habits of 400,000 Taiwanese adults the risk of coronary heart disease is about the same in people who sleep less than four hours a night as it isn't those who sleep more than eight hours a night subjects who under slept had a 35% higher risk of heart disease and people who over slept had a 34% increase another study published in 2009 followed 276 subjects for six years and found that people who slept either less than seven hours or more than eight hours where at least twice as likely to develop type 2 diabetes or trouble tolerating glucose and there's more a 2013 study of about 54,000 adults over the age of 44 found links between too much sleep and increased rates of heart disease diabetes obesity stroke and mental health issues in fact the rates of coronary heart disease diabetes and Stroke were even higher in people who overslept than in those who slept too little so the links are there sleep correlates with all kinds of health problems but it's hard to say whether too much sleep actually causes these issues it's totally possible that over sleeping is actually a symptom of things like depression or heart disease or that there's some other connection either way consistently sleeping too much might be a bad sign I guess there can be too much of a good thing I'm looking at you pumpkin pie but it's definitely the season to cozy up and start those good sleeping habits if you're not tired of hearing about your brain and sleep check out our episode on scishow psyche where Brit tells you about what you can learn from your dreams [Music] you [Music]

Channel: SciShow

Views: 395,964

Rating: 4.8984213 out of 5

Keywords: SciShow, science, Hank, Green, education, learn, aranda, michael aranda, sleep, health, insomnia, sleep walking, circadian rhythm, brain, sleep deprivation, depression, psychology, sleep apnea, cpap, sleep paralysis, glycine, muscles, rem, diet, blue light, caffine, immune system, amygdala, nap, lion, predator, prey, olivia gordon, oversleep, sleep in, can't sleep, sleepy, tired

Id: aLNhfVCa5qY

Length: 25min 22sec (1522 seconds)

Published: Thu Nov 22 2018