A lack of sleep from time to time is an unavoidable reality of life as an events professional.

When you’re working on-site it can be an around-the-clock job, and to make matters worse, this lack of sleep is often compounded by the pre-event anxiety that kept you awake the night before. According to a survey by QHotels, more than 70% of planners struggle to sleep in the run up to their events.

On top of this, you might be suffering from jetlag, if your event is being hosted in a different timezone, which can completely mess with your internal clock.

But what effect does missing out on our usual seven or eight-hour shuteye have? We take a look at the impact of sleep deprivation on the body and brain and how that manifests in our behaviour.

Related: 6 Surprising facts about what coffee does to you

  1. You lose your sense of humour

When you’re tired it can seem like an effort to even crack a smile. Research shows we become generally less emotionally expressive, but especially to amusing stimuli.

One study invited 23 people to watch funny and sad film clips before and after they were randomly assigned to a night of sleep deprivation or a normal night’s sleep.

The intensity of their facial expressiveness while viewing the films was coded by human judges and compared to their subjective emotional responses. The sleep-deprived participants demonstrated less expressiveness, and were significantly less likely to laugh or smile in response to amusing footage.

  1. You struggle to read emotions

Missing out on sleep not only makes you less emotionally expressive, it also creates difficulty reading the facial expressions of other people.

In one 2014 study 49 healthy young adults were divided into two groups, one of which spent a night without any sleep.

The next day, the subjects were asked to look at pictures and categorise emotional facial expressions as happy, sad, angry, or fearful.

The sleep-deprived subjects were slower to identify all emotional expressions and were significantly less able to accurately identify the sad faces. The research concluded that lack of sleep interferes with the brain’s ability to process emotional information.

  1. You’re less able to cope with stress

While sleep deprivation dulls our emotional sensitivity, it also impairs our emotional resilience. This makes us less able to handle stressful situations and more likely to overreact.

That’s because the amygdala, the region of the brain that alerts the body to protect itself in times of danger, goes into overdrive on no sleep, according to Matthew Walker, director of UC Berkeley’s Sleep and Neuroimaging Laboratory. This consequently shuts down the prefrontal cortex, which commands logical reasoning, and thus prevents the release of chemicals needed to calm down the fight-or-flight reflex.

Dr. Walker has found that when sleep-deprived subjects are shown disturbing images while in an MRI scanner, their amygdalae are 60% more reactive, compared to rested subjects seeing the same pictures.

And you don’t need to have been up all night to experience this – amygdala hyper-reactivity can start to occur at about 6½ hours of sleep or less.

  1. You become irritable

Erratic activity in the amygdala (integral for the processing of negative emotions) and a disconnect between the area of the brain that regulates its functions, can lead to a negative mood and decreased ability to regulate anger.

Tired people are more likely to report feelings of irritability, anger and hostility. Studies have shown that even partial sleep deprivation has a significant effect on mood. University of Pennsylvania researchers found that subjects who were limited to only 4.5 hours of sleep a night for one week reported feeling more stressed, angry, sad, and mentally exhausted. When the subjects resumed normal sleep, they reported a dramatic improvement in mood.

  1. It affects our ability to learn

Researchers from the Universities of Groningen and Pennsylvania have discovered how sleep loss negatively impacts on the brain’s ability to learn, following experiments on mice.

Science Daily reports that they deprived the mice of sleep for five hours (a period of sleep loss that is known to impair memory consolidation). The researchers observed that this significantly reduced the branching connections between nerve cells in the hippocampus.

This prevents neurons from passing signals to each other, which is vital for laying down the new memories that facilitate learning.

However, the study also found that the negative affect on the neural pathways could be reversed with as little as three hours subsequent undisturbed sleep.

  1. It impairs our memory

Missing just a single night’s sleep can seriously impair your memory. Not only can it make it more difficult to remember words and names, it can also lead to the creation of false memories say researchers at Michigan State University and the University of California.

Following a study in which participants were shown a simulated burglary in a series of images, they found that participants deprived of a night’s sleep were more likely to be unable to correctly remember the details.

“We found memory distortion is greater after sleep deprivation,” said Kimberly Fenn, MSU associate professor of psychology and co-investigator on the study, reports The Daily Mail.

Participants who were kept awake for 24 hours – and even those who got five or fewer hours of sleep – were more likely to mix up event details than participants who were well rested.

“People who repeatedly get low amounts of sleep every night could be more prone in the long run to develop these forms of memory distortion,” Fenn said. “It’s not just a full night of sleep deprivation that puts them at risk.”

  1. You can’t concentrate

The biggest thing that happens when you’re sleep deprived is that your ability to focus and pay attention slips.

According to a meta-analysis of 147 tests performed on people who had gone between 24 and 48 hours without sleep, all cognitive functions are affected including problem solving and decision-making.

This is because the brain finds it a lot more difficult to filter out relevant information from everything it picks up and to concentrate on one single stimuli (such as a person talking). In fact, going 24 hours without sleep can lead to schizophrenia-like symptoms.

A study by scientists at the University of Bonn and King’s College London found the filtering function of the brain was drastically reduced following a sleepless night.

Said Prof. Dr. Ulrich Ettinger of the Department of Psychology at the University of Bonn: “There were pronounced attention deficits, such as what typically occurs in the case of schizophrenia. The unselected flood of information led to chaos in the brain.”

Another study found that the impact of a night without sleep on your brain’s ability to focus was the same as having a 0.10% blood alcohol content.

  1. Your reaction time slows down

You are three times more likely to be involved in a car accident if you get six or fewer hours of sleep, according to the US-based National Sleep Foundation.

This is because your body is less capable of reacting quickly. A study of athletes found that while they were still able to perform athletically when sleep deprived, their reaction times were significantly affected.

Hand-eye coordination is also negatively affected in the sleep deprived but, according to one study, can be improved with caffeine!

  1. You crave high calorie food

Too little sleep may bring on a form of the “munchies”, according to researchers from the University of Chicago. They found that sleep deprivation boosted brain chemicals for appetite and caused people to crave sweet or salty high-fat foods, in much the same way cannabis does.

After several nights of poor sleep, healthy volunteers who took part in the study reached for snacks containing more calories – and nearly twice as much fat – than ones they favoured after sleeping well for the same period, reports The Guardian.

Participants had trouble resisting the snacks, even when they were full, which might explain why sleep loss raises the risk of obesity.

However, other research has indicated that eating when you should be sleeping is also a contributing factor.

“Human metabolism is closely linked with the internal clock. In circadian synchronicity, you eat and sleep when you should. If you experience circadian asychronicity, then you disrupt the links between the different layers, and this leads to metabolic consequences,” neuroscientist Akhilesh Reddy, told Business Day Live.

One example is that when some people adjust to jet lag, their bodies handle glucose — the sugars in their blood — as though they were diabetic, even if they are not.

  1. It affects your immune system

Losing sleep can seriously impair your body’s ability to fight off illness, meaning you’re more likely to get sick.

One study found that levels of white blood cells, which are a key part of the body’s immune response, fell dramatically in people deprived of sleep for 48 hours (they return to normal after a recovery sleep).

Researchers even uncovered that there’s a reciprocal relationship between sleep and your immune system, meaning you may lose additional sleep while your body fights off a bug.

Related: How to exercise in any event situation

Conclusion

Not getting enough shuteye can cause you real problems, but the good news is that the effects are not long lasting if you have an otherwise healthy sleep pattern.

However, in times of high pressure there are still things you can do to help maximise the quantity and quality of the sleep you do get. Read our guide to getting a good night’s sleep before an event.

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