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In 1965, 17-year-old high school student,[br]Randy Gardner

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stayed awake for 264 hours.

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That's 11 days to see how[br]he'd cope without sleep.

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On the second day, [br]his eyes stopped focusing.

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Next, he lost the ability[br]to identify objects by touch.

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By day three, Gardner was moody[br]and uncoordinated.

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At the end of the experiment,[br]he was struggling to concentrate,

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had trouble with short-term memory,

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became paranoid,

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and started hallucinating.

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Although Gardner recovered without[br]long-term psychological

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or physical damage,

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for others, losing shuteye can result[br]in hormonal imbalance,

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illness,

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and, in extreme cases, death.

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We're only beginning to understand[br]why we sleep to begin with,

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but we do know it's essential.

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Adults need seven to eight hours[br]of sleep a night,

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and adolescents need about ten.

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We grow sleepy due to signals[br]from our body

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telling our brain we are tired,

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and signals from the environment[br]telling us it's dark outside.

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The rise in sleep-inducing chemicals,

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like adenosine and melatonin,

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send us into a light doze [br]that grows deeper,

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making our breathing [br]and heart rate slow down

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and our muscles relax.

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This non-REM sleep is when DNA is repaired

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and our bodies replenish themselves[br]for the day ahead.

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In the United States,

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it's estimated that 30% of adults[br]and 66% of adolescents

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are regularly sleep-deprived.

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This isn't just a minor inconvenience.

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Staying awake can cause [br]serious bodily harm.

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When we lose sleep,

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learning,

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memory,

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mood,

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and reaction time are affected.

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Sleeplessness may also cause inflammation,

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halluciations,

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high blood pressure,

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and it's even been linked[br]to diabetes and obesity.

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In 2014, a devoted soccer fan died

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after staying awake for 48 hours [br]to watch the World Cup.

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While his untimely death [br]was due to a stroke,

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studies show that chronically sleeping[br]fewer than six hours a night

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increases stroke risk [br]by four and half times

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compared to those getting a consistent[br]seven to eight hours of shuteye.

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For a handful of people on the planet who[br]carry a rare inherited genetic mutation,

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sleeplessness is a daily reality.

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This condition, [br]known as Fatal Familial Insomnia,

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places the body in a nightmarish [br]state of wakefulness,

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forbidding it from entering [br]the sanctuary of sleep.

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Within months or years,

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this progressively worsening condition[br]leads to dementia and death.

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How can sleep deprivation[br]cause such immense suffering?

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Scientists think the answer lies[br]with the accumulation of waste prducts

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in the brain.

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During our waking hours,

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our cells are busy using up[br]our day's energy sources,

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which get broken down [br]into various byproducts,

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including adenosine.

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As adenosine builds up,

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it increases the urge to sleep,[br]also known as sleep pressure.

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In fact, caffeine works by blocking[br]adenosine's receptor pathways.

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Other waste products [br]also build up in the brain,

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and if they're not cleared away,[br]they collectively overload the brain

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and are thought to lead to the many[br]negative symptoms of sleep deprivation.

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So, what's happening in our brain[br]when we sleep to prevent this?

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Scientists found something called[br]the glymphatic system,

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a clean-up mechanism [br]that removes this buildup

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and is much more active when we're asleep.

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It works by using cerebrospinal fluid[br]to flush away toxic byproducts

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that accumulate between cells.

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Lymphatic vessels, [br]which serve as pathways for immune cells,

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have recently been discovered [br]in the brain,

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and they may also play a role in clearing[br]out the brain's daily waste products.

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While scientists continue exploring[br]the restorative mechanisms behind sleep,

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we can be sure that slipping [br]into slumber is a necessity

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if we want to maintain our health[br]and our sanity.