Sleep is critical to so many areas of our lives. Over the next three articles in this series I'm going to outline how sleep benefits your mind, body, and spirit.
Sleep deprivation has been linked to some of history’s most high-profile accidents:
- The grounding of the Exxon Valdez oil tanker. 11 million gallons of crude oil were spilled into Alaska’s once-pristine Prince William Sound, causing enormous ecological and economic damage.
- The accident at Three Mile Island, which remains the most significant accident in the history of the U.S commercial nuclear power plant industry.
- The Chernobyl nuclear power plant meltdown, which is considered the worst nuclear disaster in history.
- The explosion of the Space Shuttle Challenger due to a failed O-ring seal in one of its solid rocket boosters. That accident claimed the lives of seven astronauts, and set the US space program back several years.
Fatigue and inattention caused by sleep loss has been the cause of many workplace errors, reduced productivity, and serious accidents over many years – including in hospitals and onboard commercial aircraft.
Science has recognised the relationship between sleep and mental performance since the 1930’s. Concentration, reasoning, memory, and mathematical ability are all compromised by sleep deprivation.
So how does sleep affect your mind? Let’s take a look.
Learning and memory
Sleep, learning, and memory are all tightly intertwined. One hundred years’ worth of scientific study in both animals and humans has clearly demonstrated a strong link between the quantity and quality of our sleep, and our ability to learn and remember.
Sleep affects our ability to memorise and learn both before and after a new learning opportunity.
After insufficient sleep, a sleep-deprived person has more difficulty focusing their attention, which prevents efficient learning and memorisation.
The quality and quality of sleep gained after a learning session has an even greater effect. Sleep has an important role in memory consolidation, which is a major component of learning. Studies have demonstrated that getting a good night’s sleep immediately after learning and memorising a list of verbal facts, resulted in a 20-40% improvement in recall the next day compared to those who had not slept afterwards.
Clear thinking and decision-making
Along with learning and memory, sleep is important for clarity of thought and decision-making.
Studies have shown that as little as one night of sleep loss can impair innovative thinking and flexible decision-making. The harm caused by lack of sleep is particular evident in tasks that require the updating of previous plans to take account of new information.
Studies show that sleep deprivation negatively impacts our ability to make sound decisions in a (contrived) gambling context. Lack of sleep causes people to both over-estimate their expectation of gains, and downplay their losses following risky decisions.
In a simulated exercise of food and economic exchange, a sleep-deprived group was willing to spend more money on food items in the decision-making task than well-rested people were. Scientists recorded their subjects in a functional MRI while they performed the task, noting an upregulation of certain signals in the amygdala and hypothalamus that are specific to food rewards.
This deficit caused by lack of sleep will have a strong effect on body composition, which is covered in more detail in part 2 of this series.
Creativity
People often report feeling more creative in the morning after a good night’s sleep. This is supported by many studies which demonstrate that sleep promotes creative problem-solving, flexible reasoning, and insights.
Researchers think the reason for this is REM sleep, which is typically the last and longest sleep stage that a person experiences just before waking.
Acetylcholine is a brain chemical which surges during sleep, causing the neocortex and hippocampus to interact and form new connections. This can explain why we sometimes wake up in the morning having solved a problem we’ve been thinking about, or gained some new insight into something that’s been ticking away in the back of our minds. This process may be assisted by a relationship between REM and non-REM sleep, working together to create new links between existing knowledge and new solutions.
Reaction time
'Reaction time' is the amount of time taken to respond to an external stimulus. A typical person’s reaction time is somewhere between 160 and 190 milliseconds, which is less than two tenths of a second.
Reaction times increase significantly as a person accumulates sleep debt. Even low levels of fatigue can impair reaction times to the point where they become just as bad as somebody who is legally drunk.
A single night of missed sleep (an “all-nighter”) can triple your reaction time, and the recovery from this via adequate sleep can take several days.
Neurological problems
Lack of sleep can affect your mental health. Sleep is implicated in many and various mental and psychological conditions such as depression and anxiety, seasonal affective disorder, bipolar disorder, ADHD, Alzheimer's and other dementias, schizophrenia, autism, PTSD, and even suicide.
Insomnia and other sleep disorders have long been thought of as merely symptoms of psychiatric disorders. But studies now suggest that the link is bi-directional: sleep problems are a significant risk factor for - if not a direct cause of – psychiatric problems.
During deep sleep, neurons switch off and on in synchronised waves. This in turn causes blood and cerebrospinal fluid to flow back and forth like a tide, in time with these slow waves. The outflow of cerebrospinal fluid carries away toxins such as tau and beta amyloid, which naturally accumulates in the brain and can lead to Alzheimer’s and other diseases if left unchecked.
Wrapping up
It's easy to see just how important sleep is for our mental well-being. Lack of sleep can affect us in so many ways, and yet the vast majority of us simply aren't getting enough sleep.
Sleep is a skill just like any other. And just like any skill it can be learnt, practiced, and mastered.
Your virtual sleep coach,
Todd
