We’re all familiar with the foggy-headed feeling that follows a late or sleepless night. Nothing a double shot coffee won’t fix, right? But consistently falling short on your sleep quota – whether it’s from chronic sleep issues or burning the candle at both ends – can have long-reaching consequences.
“One night of short sleep won’t put you at serious risk, but lack of adequate sleep over time can be extremely detrimental to both your physical and mental health. Poor sleep has even been associated with a shortened lifespan,” says Senior Physiologist at Nuffield Health, Jade Wells.
From dealing with everyday tasks and keeping your mood on an even keel to resisting the urge to overeat, here are five key areas of our lives that are significantly impacted by sleep.
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From fending off colds and cutting heart disease risk, to speeding up our recovery from ill health, a decent sleep routine is up there with a balanced diet and regular exercise when it comes to looking after our physical health.
“Lack of sleep can suppress the immune system,” says Wells. “Certain disease-fighting substances are released or created while we sleep, so sleep deprivation can decrease the availability of these substances. This can leave us more susceptible to new viruses and bacteria.”
A disruption in our natural sleep cycle can also contribute to cardiovascular diseases: “It's not completely clear why less sleep is detrimental to heart health, but it is thought that sleeping too little causes disruptions in underlying health conditions and biological processes like glucose metabolism, blood pressure, and inflammation. This in turn can increase a person’s risk of diabetes as it is believed that sleep deficiency results in a higher than normal blood sugar level.”
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“Sleep helps your brain to work properly: while you sleep, your brain is hard at work forming the pathways necessary for learning and creating memories,” says Wells. “When we get sufficient sleep we are able to maintain normal levels of cognitive skills.”
It stands to reason then that insufficient sleep impairs these skills. And even a small sleep deficit can make a difference:
“In lab settings you could detect the difference between an individual who had slept well and an individual who has had just two hours less sleep than they would normally have” says John Groeger, Professor of Psychology at the University of Hull
. “And it’s the most difficult stuff – decision making, thinking clearly, making evaluations and judgements – that will suffer most. That, and your ability to concentrate and focus.”
For one-off tasks we might be able to wing it but it’s when we need to repeatedly call on our cognitive skills or use them for sustained periods that we can run into trouble:
“If you have to do a one-off task, and you understand you have to do it and you know it’s coming up, even if you’re very tired, you’ll be able to manage," says Professor Groeger. "But you might not manage to do it twice. And when all that energy is going to the difficult decision other things may suffer during that moment – so this isn’t cost-free in any sense.”
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“Most people probably know from their own experience that when they have a bad night’s sleep, they often feel more emotional the next day – they might find themselves more prone to crying over something they wouldn’t normally, or to snapping at someone who irritates them,” says sleep expert and Lecturer in Psychology at the University of East London
, Josie Malinowski.
“This common experience is backed up by scientific research – for example when people are deprived of sleep in a lab, their reactions to negative stimuli the next day increase, compared to if they were allowed to sleep.”
But it’s not just our negative emotions that are heightened: “What is probably less well-known is that this emotional over-reactivity that happens when we’re sleep deprived happens for positive emotions as well as negative ones – so although we might be more irritated when someone annoys us after a bad night’s sleep, we would also react with more joy when something good happens.”
But while the highs might seem like a thrilling prospect, this rollercoaster of emotions can come at a high price. When experiencing high levels of emotion on a daily basis becomes a chronic condition, “an individual’s risk of developing mood disorders, such as anxiety or depression is increased,” warns Wells.
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It’s not surprising we’re more likely to get caught with our hand in the cookie jar when we’re feeling tired. Sugary snacks not only offer us a quick hit of energy, they can be just the perk you need when you’re struggling to get your brain in gear.
“It’s harder to make all sorts of decisions well when we’re sleep deprived. We feel we need a boost in order to get through – and it’s going to be the quick-hit stuff that we go for,” says Professor Groeger.
But it’s not just a lack of willpower that pushes us to give into these cravings: “The drive we have to eat, and the ability to stop eating when we realise we should stop, are controlled by two hormones: Leptin and ghrelin,” he adds.
“If we’re not sleeping very well, the signal to stop gets ‘quieter’, as it were, and the signal to eat gets ‘louder’. So, both of the things you need in order to exercise control get messed up by sleep loss.”
And even small amounts of sleep loss can make a difference: “We’re talking about a lost night here. So over the course of a week it’s not surprising, if people aren’t sleeping well that they would gain weight.”
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Heightened emotions, increased sensitivity and irritability, more difficulty controlling anger – it’s not surprising the emotional fallout of sleep deprivation can take its toll on our relationships.
Researchers at University of California, Berkeley, found that a bad night’s sleep exacerbated conflict between partners
. In one experiment, 78 young adults in romantic relationships provided daily reports over a two-week period about their sleep quality and relationship stresses. Overall, participants reported more discord with their partners on the days following a bad night’s sleep.
In a second study, 71 couples discussed a source of conflict within their relationship. Those who had slept poorly reported more negativity toward one another.
And it’s not just those close to us who are affected by sleep deprivation. A study by the Medical Institutet Karolinska in Stockholm, Sweden, found that lack of sleep also affects our perceived approachability
to new people, making us more socially repellent.