What would happen if you didn't sleep?

In 1965, 17-year-old high school student Randy Gardner stayed awake for 264 hours—11 days—to see how he'd cope without sleep. On the second day, his eyes stopped focusing. Next, he lost the ability to identify objects by touch. By day three, Gardner was moody and uncoordinated. By the end of the experiment, he struggled to concentrate, had trouble with short-term memory, became paranoid, and started hallucinating. Although Gardner recovered without long-term psychological or physical damage, others may experience hormonal imbalances, illness, and, in extreme cases, death from sleep deprivation.

We are only beginning to understand why we sleep, but we know it's essential. Adults need seven to eight hours of sleep a night, and adolescents need about ten. Sleepiness occurs due to signals from our body indicating fatigue and environmental cues that it’s dark outside. The rise in sleep-inducing chemicals like adenosine and melatonin sends us into a light doze that deepens, slowing our breathing and heart rate and relaxing our muscles. This non-REM sleep is when DNA is repaired, and our bodies replenish themselves for the day ahead.

In the United States, an estimated 30% of adults and 66% of adolescents are regularly sleep-deprived. This isn’t just a minor inconvenience; lack of sleep can cause serious bodily harm. When we lose sleep, our learning, memory, mood, and reaction time are affected. Sleeplessness may also cause inflammation, hallucinations, high blood pressure, and has been linked to diabetes and obesity. In 2014, a devoted soccer fan died after staying awake for 48 hours to watch the World Cup. While his death was due to a stroke, studies show that chronically sleeping fewer than six hours a night increases stroke risk by four and a half times compared to those getting a consistent seven to eight hours of sleep.

For a handful of people with a rare inherited genetic mutation, sleeplessness is a daily reality. This condition, known as Fatal Familial Insomnia, places the body in a nightmarish state of wakefulness, preventing sleep. Within months or years, this progressively worsening condition leads to dementia and death. How can sleep deprivation cause such immense suffering? Scientists believe the answer lies in the accumulation of waste products in the brain. During our waking hours, cells use up energy sources, breaking them down into byproducts, including adenosine. As adenosine builds up, it increases the urge to sleep, known as sleep pressure. Caffeine works by blocking adenosine’s receptor pathways.

Other waste products also build up in the brain, and if not cleared away, they collectively overload the brain, leading to the many negative symptoms of sleep deprivation. So, what happens in our brain when we sleep to prevent this? Scientists have discovered the glymphatic system, a clean-up mechanism that removes this buildup and is much more active during sleep. It uses cerebrospinal fluid to flush away toxic byproducts that accumulate between cells. Recently discovered lymphatic vessels in the brain, which serve as pathways for immune cells, may also help clear out the brain's daily waste products.

While scientists continue to explore the restorative mechanisms behind sleep, we know for sure that slipping into slumber is a necessity to maintain our health and sanity.