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While few people, thankfully, will have experienced the kind of physical or psychological effects associated with severe sleep deprivation, most people in demanding work roles and – indeed – anyone that has raised children will be acutely aware of the impact that even a moderate amount of tiredness can have on a their mood and levels of stress.

There is some irony that, while the Geneva Convention prohibits interrogators from undertaking acts that would deprive a prisoner of sleep in war, consistently burning the midnight oil is still seen as a badge of honour in business.

Myths abound around how much sleep people can get by on. Margaret Thatcher’s image was reinforced by her (in)famous ability to get by on just four hours a night. Perhaps inspired by the Iron Lady, it has been reported that Donald Trump claims he needs just three.

Entire industries from the City of London to Silicon Valley have been defined in part by macho long-hours / high-stress cultures; the success of these sectors has been achieved at a high price.

Less than 3% of people can operate well on a consistently small number of hours sleep. The vast majority of us need somewhere around eight hours good sleep each night, though it is still regarded as ‘normal’ to sleep between 4 and 12.

Lack of sleep can quickly have as damaging an effect on people’s ability to concentrate and perform as significant levels of alcohol can.

But while a boozy lunch on work time is no longer seen as acceptable, it is probably safer to be drunk than sleep impaired once you hit a certain level.

At its extremes tiredness has played a factor in many major disasters over recent decades. Hundreds of people are killed every year on British roads as a result of people falling asleep at the wheel.

Neuroscience shows that even beyond matters of life and death, lack of sleep is bad for business.

It is probably safer to be drunk than sleep impaired once you hit a certain level.

The dorsolateral prefrontal cortex, an area of the brain responsible for decision making, working memory and planning, hibernates during sleep, allowing mental connections and creative associations to occur.

The importance of sleep in learning

Having a good sleep after learning something new also improves the chances that we will remember it in a way that makes it practical.

The brain has free rein while we are asleep to sort through the information it has taken in during the day and decide what is important. The sleeping brain sorts and connects information without the distractions or justifications of a conscious mind.

Insufficient sleep means we are not giving our brains time to integrate information in a meaningful way and are therefore operating at a suboptimal level.

Day-to-day decision making, problem solving and creativity become much more difficult when we are sleep deprived. It also becomes harder for us to regulate our emotions and handle stress.

Do you know about the amygdala?

The amygdala, which lies inside the brain’s temporal lobes and regulates our emotions, emotional behaviour and motivation, often over-reacts when sleep-deprived and causes people to respond over-hastily.

We’ve also seen how tired children respond differently to rested children in given situations; the same effect is true – albeit generally more measured – in adults.

Research undertaken by the NeuroLeadership Institute and its faculty member Professor Jessica Payne has shown that sleep levels are closely related to stress and mood, and that good sleep is one of three key states required for the human brain to maintain its resilience and perform optimally.

The role of fatigue in stock market value

When the former CEO of Lloyds Bank stepped down citing stress and “extreme fatigue”, it wiped almost a billion off the bank’s market value, and the world of business became more acutely aware of just how damaging such things can be to a company’s performance and reputation.

In my experience, working with executives over many years and researching executive stress, it is clear that we all experience some level of stress in our lives and business leaders must be adept at managing and mitigating stressful situations on a daily basis if they are to have any sort of career longevity.

Neuroscience shows that the brain works at its best under moderate levels of stress. If stress is too high we become anxious and can’t process information properly. If they are too low, our brains tend to relax and we can miss information coming through.

Small, positive social signals such as a smile or a pat on the back can cause others to see a challenge more positively

Neuroscience shows that good sleep is crucial for optimal brain function, alongside a moderate level of stress and positive affect (positive mood). These elements are intrinsically related.

Cortisol, a life sustaining adrenal hormone known as the “brain’s stress chemical”, is released to combat the weariness of sleep deprivation. However, its accumulation is damaging for performance.

Positive affect refers to the extent to which an individual subjectively experiences positive moods such as joy, interest, and alertness. Moods are contagious. Small, positive social signals such as a smile or a pat on the back can cause others to see a challenge more positively, stimulating greater creativity and willingness to contribute to team efforts.

Poor sleep affects our mood and makes us more stressed. A bad mood tends to make sleep and stress worse. When we have high levels of all three we experience significant cognitive impairment, with further negative impacts on basic perception, judgment and decision-making.

High levels of ongoing stress can also create permanent damage to the hippocampus, the brain region responsible for memory.

Given the increasing stresses and demands on our time associated with doing business in an increasingly chaotic, complex and global trading environment, leaders need to understand the limits of their brains and their own personal needs. The better they can manage their sleep, stress and mood levels, the better they will be at leading others.

A bad mood tends to make sleep and stress worse.

Getting enough sleep is vital first step if we are to perform to the highest level. We’ve already spoken about how most people need around eight hours of good sleep a night on a regular basis.

Other strategies can help too.

Taking a 20 minute nap, going offline for a short period of time each day for meditation or simply taking a walk regenerates our creative brain circuits, improves memory, helps us make connections and enhances mood.

Thinking too hard about a problem can make it harder to solve and it is often better to let the mind wander and allow the brain’s unconscious processors to take over.

Rather than driving their teams relentlessly towards a goal, leaders should be aware of the need for rest and de-stressing, and sympathetic enough to see time-out as an opportunity to relax and reinterpret problems, rather than simply wasted time.