Experts recommend 7-9 hours of sleep a night. But how much sleep do you really need? Many of us swear by a good night’s rest, while others claim to function just fine on a few hours.
While it’s true humans operate on different circadian rhythms, resulting in varying needs and intensities of sleep, we’re notoriously bad at noticing when we’re sleep deprived.
A lack of sleep causes poor mood, bad decision, and delayed reaction time in the short term. In the long-term, sleep deprivation has been associated with heart failure, hypertension, and diabetes. This guide goes uncovers how long we can stay awake before things go south, the consequences of sleep deprivation, and whether or not sleep loss is lethal.
How Long Can A Human Go Without Sleep?
There’s little evidence on the exact length one can go without sleeping. There’s even some debate as the longest a human has ever stayed awake. In the 1978 edition of the Guinness Book of World Records, it states that Maureen Weston held the record for voluntary wakefulness at 14 days and 13 hours. The most notable of sleep deprivation, however, belongs to Gardner.
After just two days without sleep, his vision began to lose focus, his speech began to slur, and he found difficulty identifying objects by touch. The next day, he became even more uncoordinated and moody. Finally, by the fifth day, he began to hallucinate.
John Ross, the medic responsible for monitoring him, noted that by day 11, he appeared expressionless, struggled to respond to simple questions, and would forget what he was doing mid-activity.
However, neither he nor Weston ever suffered any long-term physical effects akin to the sleep-deprived animals. Science suggests this may be a result of an evolved human ability to microsleep. Similar phenomena have been observed in fish and birds, who can essentially shut down one hemisphere of the brain to sleep with one eye open. Birds can even detect predatory danger while half of their brain snoozes. It’s postulated that humans have developed something similar known as microsleep as we evolved to endure.
What is Microsleep?
Microsleep refers to a short, unintentional period of drifting off to sleep. It may be characterized by a quick head snap as you nod off trying to pay attention to something boring. Most often, however, microsleep can occur in a person without their knowledge and eyes wide open.
Although periods of microsleep typically result from forcing oneself awake during normal sleeping hours, prolonged sleep debt contributes to their frequency. They can last from the briefest of seconds to a few minutes and are the body’s way of catching up on much-needed rest. By involuntarily shutting down, humans have evolved to avoid total sleep deprivation throughout long periods of wakefulness.
However, spontaneously drifting off to sleep isn’t harmless. If it happens sitting on the couch or at your desk, consequences are small. But if sleep deprivation causes microsleep while driving, caring for children, or handling dangerous machinery, consequences could be dire.
Lack of Sleep Symptoms
Microsleep, therefore, represents a dangerous symptom of lack of sleep. Spontaneous eye-closures become more frequent, especially during monotonous tasks, and it’s scary to think they can happen without our knowledge. Unfortunately, humans can’t count on constant stimulation to avoid other behavioral and psychological consequences.
Don’t think a lack of sleep is affecting you? You’re probably a poor judge of your sleep-related impairment. Impairment from lack of sleep is strikingly similar to being drunk. Despite our own reassurance that we’re fine, science says that when sleep-deprived, our cognitive decline shines through. Sustaining attention and maintaining normal behavior requires sleep health, whether we like to admit it or not.
When researchers took an fMRI scan of sleep-deprived participants, they observed transitional stages of consciousness in visual, auditory, and somatosensory cortices. According to their brain waves, participants were sitting at the crux of sleep and wakefulness. In another study, subjective sleepiness ratings were taken during chronic sleep restriction (0, 4, or 6 hours per night over 2 weeks). Although participants only narrowly rated feeling sleepier with fewer hours, there was a linear relationship of behavioral alertness to the amount of sleep. Total sleep deprivation showed disproportionate negative neurobehavioral responses during wakeful periods when compared to any amount of sleep.
Lack of Sleep Short-Term Dangers
In the short term, insufficient sleep is clearly associated with loss of attention and performance. Outside of behavioral change, sleep disruption is associated with sympathetic nervous and adrenal activity. The short-term consequences of not sleeping produce a greater stress response in the body, keeping us from relaxing even when we want to. These metabolic changes produce chronic inflammatory responses and reduced quality of life. Not to mention, being constantly stressed come with massive consequences for mood and emotional distress.
The dangers of losing sleep in the short term include, but are not limited to:
- Decreased mood
- Depression and anxiety
- Chronic inflammation
- Increased adrenal activity
- Loss of attention and focus
- Decreased performance on tasks
- Loss of reaction time
- Poor glucose metabolism
- Elevated resting heart rate
- Somatic pain
Lack of Sleep Long-Term Dangers
If insufficient sleep can alter hormonal regulation, that has downstream effects on glucose metabolism and blood pressure. Poor insulin sensitivity and high blood pressure might not be dangerous in the short term, but these chronic conditions lead to cardiovascular risk factors such as diabetes, stroke, heart attack, and even death.
When it comes to the brain, we’ve shown sleep loss can change task-related activity involving memory, executive function, and memory. In a more shocking result, science has shown sleep loss can completely alter brain structure. A 2014 study in Neuroreport tested regional gray matter in healthy adults after about 72 hours of total sleep deprivation. Their results found a significant loss of gray matter in the thalamus. While overall whole brain gray matter volume remained intact, thalamic regions clearly suffered.
Another study tested chemical levels after 21 days of total sleep deprivation. As it would be unethical to force sleep deprivation in humans for 21 days, this study was conducted on rats. When compared with control groups, sleep-deprived rats showed impaired maintenance of long-term potentiation and balance between antioxidant defenses of the hippocampus.
Probably the most dramatic result from a murine study comes out of the Journal of Neurochemistry. Researchers testes gene transcription in rats deprived of sleep for only a week. Seventy-five different transcripts showed increased expression when compared to controls. These included gene transcripts responsible for coding stress response proteins, immunoglobulins, cortistatin, and more. Sixteen specifically decreased their transcription, such as coding for type I procollagen and dihydrolipoamide acetyltransferase.
In layman’s terms, one week of sleep deprivation altered the genetic ability to code molecules responsible for immune system function, stress management, connective tissue, and metabolism. According to this research, losing sleep can have consequences at the molecular level.
In summary, the common long-term consequences of lack of sleep include:
- Gastrointestinal disorders
- Type 2 diabetes
- Weight gain
- Reduction in thalamic gray matter volume
- Metabolic syndrome
- Reduced antioxidant defense
- Heart disease
- Increased cancer risk
- Potential molecular and genetic changes
Can You Die from Lack of Sleep?
So far, nothing has proven that you can die simply from a lack of sleep. Due to the evolved ability to microsleep, even the most sleep-deprived individuals will involuntarily drift off into restorative states. Humans are surprisingly resilient to lack of sleep when it comes to survival.
Our sleep deprivation issues are largely psychological – meaning we mostly experience loss of focus and hallucination with total sleep deprivation. In animals, lack of sleep has been shown to result in death. Studies suggest not sleeping for 9-77 days in dogs, 4-31 days for rabbits and only 3-14 days in rats can cause sudden death. That being said, due to size and metabolic differences, it would theoretically take a human up to six times as long to experience results this drastic.
No human has stayed awake for hundreds of days at a time, and research ethics wouldn’t allow for it in any study. Even in theory, by that point, a person would be so hallucinogenic and sick that they’d either be rushed to the hospital or fall asleep involuntarily.
However, you can definitely die from the consequences of losing sleep. Hypertension, cardiac failure, stroke, and increased cancer risk are notoriously deadly. Even in the short-term, falling asleep at the wheel or in dangerous situations can kill you. It may not be proven that a human can die from lack of sleep, but it absolutely increases risk factors for mortality.