Miya Pearson
Sleep is essential for our physical and emotional well-being. But what happens when we go without it? After two days (48 hours) of no sleep, the body begins to experience physical symptoms of sleep loss. The immune system is impacted, with natural killer cells (responsible for fighting tumours and viruses) decreasing by 37% after 48 hours of wakefulness, according to one study. Visual hallucinations can also occur, as images form incorrectly on our retinas. These may be benign, such as believing a room is larger than it is, or frightening, such as the sudden appearance of an imaginary person or animal.
| Characteristics | Values |
|---|---|
| Time without sleep | 48 hours |
| Impact on health | Extreme sleep deprivation |
| Cognitive performance | Worsened |
| Fatigue | Very high |
| Microsleeps | Likely |
| Perceptual distortions | Likely |
| Irritability | Increased |
| Temporal disorientation | Likely |
What You'll Learn
Hallucinations and impaired vision
Sleep deprivation can lead to hallucinations and impaired vision. After one night without sleep, individuals may experience blurred vision and diplopia, with the visual complaint progressing gradually from distortions to illusions, and finally, hallucinations. The visual modality is the most commonly affected, followed by the somatosensory and auditory modalities.
Hallucinations
About 80% of people will hallucinate if they've been severely sleep-deprived. "Severe" means getting only a few hours of sleep over one night or going several days without sleep. Most of these incidents involve visual hallucinations.
Impaired Vision
After 24 hours of sleep deprivation, individuals may experience impaired coordination and memory. After 48 hours, the brain will start entering brief periods of complete unconsciousness, also known as microsleep.
Sleep deprivation can also cause a "tunnel-vision" effect, where attention is restricted to the centre of the visual field. This may be caused by sympathetic arousal.
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Increased stress hormones
Sleep deprivation and stress are closely linked in a vicious cycle. Sleep loss can lead to an increase in stress hormones, which can, in turn, disrupt sleep.
The stress-sleep cycle
Sleep and the stress response share the same pathway: the hypothalamic-pituitary-adrenal (HPA) axis. When something disrupts the HPA axis functions, it can disrupt your sleep cycles.
Sleep and the HPA axis
The HPA axis includes the hypothalamus and pituitary gland in the brain, and the adrenal glands, which sit on top of the kidneys. The HPA axis releases a cascade of hormones, including cortisol, the body's primary stress hormone. Cortisol helps the body respond to stress and has a powerful influence on sleep and waking in the human body.
Sleep deprivation and the HPA axis
Studies have shown that insomnia and other forms of sleep deprivation cause the body to secrete more cortisol during the day, perhaps in an effort to stimulate alertness.
Stress and the HPA axis
When the body experiences a stressful event, the brain activates the HPA axis, which releases cortisol. Glucocorticoids, such as cortisol, are essential for the body's adaptive response to stress. However, chronic or ongoing stress can lead to long-term effects on the HPA axis and cortisol levels.
Sleep deprivation methods and the HPA axis
Many methods of sleep deprivation, such as sleep restriction and sleep fragmentation, have been shown to increase cortisol levels. However, some studies have shown that when the experimental conditions are designed to avoid stress, sleep deprivation does not always increase cortisol levels.
Stress-associated consequences of sleep deprivation
The activation of the HPA axis during sleep deprivation might have multiple physiological and behavioural effects. Sleep loss, and in particular the suppression of REM sleep, can affect physiological and behavioural stress coping mechanisms.
Reducing stress in sleep-deprivation studies
Given the complex and reciprocal relationship between sleep and the HPA axis, it is challenging to separate the consequences of sleep-deprivation procedures from the stressful protocol-related external stimulations. However, recent progress in biotechnological tools, such as chemogenetics and optogenetics, as well as improved automated real-time sleep-scoring algorithms, could provide novel, less stressful ways to study sleep.
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Microsleeps
After 48 hours without sleep, you will likely experience microsleeps—brief episodes of sleep lasting a few seconds, during which you lose conscious control of your performance. Microsleeps can be dangerous, especially if they occur in situations that demand constant alertness, such as driving or operating heavy machinery.
During microsleep, your brain rapidly shifts between being asleep and awake, with each sleep period lasting only a few seconds. You may experience multiple microsleep episodes in quick succession as you struggle to stay awake.
- Droopy eyes
- Slow eyelid closure
- Head nodding
- Excessive yawning or blinking
- Lack of awareness of your surroundings
- Difficulty processing information
The primary risks associated with microsleep are accidents that could occur while engaging in sensitive tasks requiring constant alertness. Driving during microsleep is particularly dangerous, as even dozing off for a few seconds can cause you to travel a significant distance in the wrong direction, leading to a potential collision.
Chronic microsleep can also have negative consequences beyond the immediate risks, including decreased worker productivity, increased likelihood of absenteeism from work, and a higher risk of developing sleep disorders or other medical issues.
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Cognitive impairment
Sleep deprivation can have a significant impact on cognitive function, and this impairment becomes more severe the longer a person goes without sleep. After two days—48 hours—without sleep, a person's cognitive performance will have worsened, and they will be very fatigued.
At this point, the brain will be experiencing microsleep, brief periods of complete unconsciousness that can last for several seconds. A person might also start to experience complex hallucinations, where they see, hear, or feel things that aren't there. These hallucinations can be multisensory and may be hard to distinguish from reality.
Research has also shown that after 30 hours of sleep deprivation, people struggle to recognise emotions, such as anger and happiness. This cognitive impairment can also lead to difficulty in social situations, where a person might misinterpret social cues.
After two days without sleep, a person's perception of reality may be distorted, and they may experience temporal disorientation. They may also feel an overwhelming urge to sleep, and their immune system will be compromised, with inflammatory markers circulating at increased levels.
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Mood swings and anxiety
Sleep deprivation can have a significant impact on mood and anxiety levels. After just one night of poor sleep, a person may experience increased irritability, stress, anger, sadness, and mental exhaustion.
The effects of sleep deprivation become more severe as the duration of sleep loss increases. After 48 hours without sleep, individuals are likely to experience increased irritability and temporal disorientation, in addition to perceptual distortions and an overwhelming urge to sleep.
Chronic sleep deprivation has been linked to the development of mood disorders such as anxiety and depression. Studies have found that individuals with insomnia are up to 20 times more likely to develop anxiety disorders and are at a higher risk of experiencing panic attacks. Sleep deprivation can also worsen existing mental health conditions, creating a cycle that further exacerbates sleep loss.
The impact of sleep deprivation on mood and anxiety is bidirectional, with anxiety increasing arousal and making it more difficult to fall asleep. This can lead to a vicious cycle where anxiety contributes to sleep deprivation, which in turn heightens anxiety levels.
Addressing sleep problems is crucial for managing mood disorders and anxiety effectively. Improving sleep habits and adopting good sleep hygiene practices can help alleviate the severity of psychiatric disorders. This includes maintaining a consistent sleep schedule, limiting exposure to bright lights and electronic devices before bedtime, and engaging in regular physical activity.
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Frequently asked questions
After 48 hours without sleep, most people have difficulty staying awake and experience "microsleeps", which are brief periods of light sleep that can last up to 30 seconds. During these microsleeps, the brain is in a sleep-like state. After two days of no sleep, you may also experience blurry or double vision, which may progress into distortions of reality and hallucinations.
If you need to stay awake after two days of no sleep, you can try drinking water, getting sunlight, and consuming caffeine. However, it's important to note that there are no long-term strategies to effectively function on little to no sleep.
Staying awake for two days can have several negative consequences, including impaired decision-making, vision and hearing impairments, decreased hand-eye coordination, increased muscle tension, and a higher risk of accidents. It can also lead to cognitive impairments, changes in mood, and difficulty in performing complex tasks.
