-- Navy SEALs may be some of the toughest people on the planet, but even an elite soldier doesn't do well without sleep.
Stew Smith, a former Navy SEAL, said he survived for three days on no sleep before the hallucinations started to set in. After about 72 hours of sleep deprivation during training, Smith recalls mistaking an airplane for a flying horse, perceiving a bridge as a giant Pez dispenser, and seeing a squat, muscular body builder where there was in fact a fire hydrant.
But he wasn't quite done. Smith and his crew had another two days of running, swimming, paddling, climbing and plunging into freezing water. In total, he and his team had to stay awake for a punishing five days as part of their Navy SEAL training.
“I would be thinking of something and I would see it in front of me like a cartoon character,” he recalled, describing his hallucinations. “When you’re losing sleep, after a while you turn to this fight-or-flight response. You just go into survival mode.”
At the time, Smith said he survived by staying in constant motion, staying uncomfortable, and psychologically breaking each day into a series of six-hour stretches until the next meal.
While SEALs may need to stay awake for days in life-or-death situations, Smith said he would never wish this kind of sleep deprivation on anyone. ABC News' own Dan Childs, head of the Medical Unit, is currently staying up for 40 hours as part of the "Good Morning America" 40th anniversary event to show how important sleep is. That's half of the time Smith was required to stay up.
Dr. Kirk Parsley, another former SEAL who is also a physician specializing in sleep health, couldn’t agree more.
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While SEAL training didn’t break him, Parsley said he was almost brought down by the chronic sleep deprivation that accompanied his time in medical school and residency.
“I had extreme chronic anxiety, I was super emotional and impulsive, I couldn’t manage my appetite or keep a good workout regimen,” he said. “All the metrics people measure their success by ... I was suffering in all of them." It wasn’t until he began prioritizing sleep that he felt like he regained control of his mental and physical wellness.
For some reason, he emphasized, people are very resistant to the idea that sleep is truly crucial to health.
But sleep is no joke. When people become sleep deprived, they experience cognitive slowing, impulsiveness, moodiness, a diminished immune system, and an accumulation of waste products in the brain and body, according to Dr. Charles Czeisler, the chair of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital.
During sleep, Czeisler explained, cells in the brain shrink temporarily. This allows the “drainage tubes” of the lymphatic system to expand and remove more toxins from your body.
“When you’re awake, brain cells remain tight and the brain can’t get rid of these toxins efficiently,” he said.
That’s why people who are sleep deprived are susceptible to headaches, and part of why those who have stayed awake for 24 hours perform similarly to those with a blood alcohol content of 0.1 percent on many mental and physical tasks, he noted.
The consequences of sleep deprivation don’t stop there. Without sleep, stress hormones, like cortisone, rise and weaken your immune system. If one doesn’t sleep enough the week prior to getting a flu shot, his or her body will produce many fewer antibodies, which makes the vaccine much less effective, Czeisler noted.
To make matters worse, your odds of catching a cold skyrocket with poor sleep.
And if you think coffee is the cure, think again. Czeisler explains that coffee accomplishes none of the crucial functions of sleep (like solidifying memories or removing waste) -- it merely blocks the receptors that alert your brain to the depletion of energy you’re experiencing. You’ll briefly feel less “sleepy,” but your body needs sleep just as badly.
An estimated 50 to 70 million Americans have chronic sleep disorders, according to the Centers for Disease Control and Prevention, and nearly 40 percent of adults report falling asleep without meaning to at least once a month. In that vein, the U.S. Department of Transportation estimates drowsy driving to be responsible for 1,550 fatalities and 40,000 nonfatal injuries annually in the United States.
It’s no surprise that Americans have so many sleep troubles, Czeisler said, especially with constant exposure to the blue light from computer screens and mobile devices disrupting our circadian rhythms. That, combined with workaholic tendencies, can be a recipe for disaster, he said.
To improve sleep hygiene, Americans can try to go to bed at the same time each day, get those phones out of the bedroom, make sure sleep environments are dark, quiet and cool -- and most importantly, take the crucial first step of deciding that sleep matters.
“Your health, well-being, longevity and success can really be broken down into four pillars: sleep, nutrition, exercise and stress mitigation,” Parsley said. “These four are all equally important -- like the tires on a car. Would you take off one of your car tires? None of those tires are optional.”
So unless you're pulling a stunt like ABC News' Dan Childs -- for the sake of science and in a carefully monitored sleep lab -- put down the screen you're reading this on, put on your PJs, and go get some sleep.