The scientific evidence is clear: Getting enough quality sleep is vital for the optimal functioning of both the brain and the body! Yet, for surprisingly many of us a good night’s sleep is elusive. Epidemiological data indicate that about a third of people experience sleep problems, with around 10% of the population suffering from chronic lack of sleep. As we start the new year, now might be a good time to take a closer look at the important role sleep plays in keeping us well and, as the scientific evidence I review here shows, resolving to sleep more this year is probably the best New Year’s Resolution you can make and, in any case, is sure to pay handsome dividends! In fact, I am so convinced of the importance of improving sleep health, that I plan to devote this and the next two posts to sleep.
The rest of this post draws on many sources to review some of the reasons why sleep plays such an important role in our lives. I present a snapshot of some of the research on sleep’s benefits and the costs to our mental health and well-being of not sleeping enough. The next post is planned to provide a summary of what sleep scientists have learned about sleep, its functions, and the neuroscience of sleep. In the final post in this series, I will take a closer look at sleep disorders, their treatment, and provide a detailed set of some pointers on how to sleep better. But what better place to start than to ask yourself one of the most important questions about your health that you possibly can.
Are you getting enough sleep?
The American National Sleep Foundation recommend that most adults get between 7 and 9 hours of sleep per night. They recently published the results of a panel of experts who derived a set of detailed sleep quality guidelines based on state of the art scientific research. The results were published in 2017 in Sleep Health, a scientific journal. The sleep experts agreed that what counts as good sleep is not the same for everyone. In particular, the indicators for quality sleep differ across the age range: For instance, older adults (65+) may take longer to fall asleep than younger people, have more frequent night time awakenings, and show differences in the various phases of sleep compared to children and adults.
Here is a sample of some of the other indicators of poor sleep quality in adults with figures for over 65’s and younger age groups specified separately:
- Sleep latency (the time it takes to fall asleep): More than 45 minutes (60 minutes or more)
- Night-time awakenings for longer than 5 minutes: More than 3 (except for teenagers: More than 2)
- Number of naps per 24 hours: More than 3 for adults and older adults (More than 2 for children and teens)
If any of these are true for you, then you are most likely not getting adequate quality sleep. You should also allow yourself the opportunity of at least 8 hours of good quality sleep per 24 hour period according to Matthew Walker, author of the bestselling, “Why we sleep: the new science of sleep and dreams.”
Why sleep matters so much: What you gain from having enough, and what you lose from sleeping too little.
We spend about one third of our lives sleeping, so what difference does a few hours here or there make in the bigger scheme of things? Quite a lot, so it turns out. Over the past 50 years, scientists have unearthed some intriguing evidence on the power of sleep, and the consequences of inadequate sleep in humans.
It turns out that sleep plays a key role in helping our brains to consolidate memories, a good night’s sleep can improve learning and creativity, and helps us to feel better, perhaps even to process traumatic experiences more effectively. Good sleep quality also turns out to be a key ingredient of quality of life in old age and may be a key component of longevity. On the other hand, lack of adequate sleep is associated with poor mental health, accidents on our roads and in workplaces, and even increased cardiovascular risk!
These are far reaching claims indeed, but there is a growing body of increasingly solid, high quality research that backs up all of these claims regarding the benefits of good sleep and the costs of poor sleep. In fact, I am presenting only a small sample of the data on the immense importance of sleep and the far-reaching health and other consequences of inadequate sleep.
Sleep is good for you: stacking up the benefits
Sleep and learning
In a remarkable series of experiments, neuroscientist, Matthew Walker and his co-workers tested the role of sleep in learning. They first required their participants to learn a taxing 100 face-name pairs and tested them, then they divided the participants into two groups. One group was asked to take a 90 minute nap, while the other was kept occupied in the laboratory with menial tasks. Later that day, both groups again performed a similarly taxing learning task and had their performance measured. The researchers were interested in whether taking a nap impacted on how effectively participants could absorb new information after having already been exposed to a challenging learning task. From no differences between the groups on their learning performance at the start, the napping group obtained an amazing 20% better scores than the no nap group on the second trial.
From analysing data on the electrical activity of the brain gathered from the nappers during their sleep, the researchers developed the theory that during some of the stages of sleep, the brain transferred information from short term memory which has a limited capacity to long term memory, thus both consolidating “old” learning and refreshing the brain’s capacity for new learning. Other research on the benefits of sleep for retention has shown between 20 and 40% advantage in retention for those who sleep after learning new information, with deeper sleep (of which we tend to get more in the first half of the night) directly associated with better recall. Similar benefits occur for people who sleep after learning new motor skills – a nights good sleep after practice aids in memory consolidation and performance.
The study mentioned above – and many others – have shown that certain phases of sleep have a role in transferring information from short term memory into long term storage. But sleep (and dreaming) also has a key role in creativity and problem solving as is illustrated by many anecdotes of scientific discoveries that originated in dreams. One famous example is the discovery in 1865 of the benzene ring, one of the most important structures in organic chemistry, by the German chemist Kekule who related that the structure of the hydrocarbon ring came to him in a dream where he saw carbon atoms connect up in long chains and move around in snake like fashion. Then he saw one of the snakes start to eat its own tail – which was the dream image that lead him to realize the cyclic structure of benzene.
Another, perhaps lesser known example, is that of Elias Howe who is credited with inventing the mechanical sewing machine. One of the key innovations that make mechanical sewing possible is having the hole in the needle at the tip rather than at the back of the needle: This innovation came to him when he dreamt that he had been captured by cannibals who were dancing around him waving their spears – and these particular spears had holes at the pointy tips which moved up and down with the tribal dancers’ movements.
Both of these examples of “dreamt up” creative solutions to seemingly intractable problems, involved forging connections between seemingly unconnected ideas or images, in other words, creating associative webs between disparate concepts. It turns out that REM sleep, the period of sleep where our eyes move rapidly and when we are most likely to dream vividly, plays a key role in generating and strengthening webs of association in the brain.
Matthew Walker, the neuroscientist mentioned earlier, and his team have started to gather compelling evidence that is beginning to prove the power of dream sleep to enhance our creativity.
Using the phenomenon of sleep inertia, the carry-over of brain processes from a sleeping state to the waking state for brief periods following being awakened, researchers devised a very short anagram-based test of creative problem solving that took no more than 90s. By waking participants up during different physiological stages of sleep, and administering the test, they believed they could gain access to the brain processes that characterise that sleep stage and test out how the brain approaches problems during the different phases of sleep.
Participants were given some practice prior to going to sleep and their sleep physiology were monitored throughout the experiment. The results were striking: In comparison to daytime performance and performance following being awoken from deep, non-REM sleep, participants solved between 15 and 35% more anagrams just after being awoken from REM sleep. They also reported that after REM sleep, they found the solutions to the problems just “popped out”, while at other times, the anagrams required more deliberate and conscious effort.
Other researchers found similar results using a range of research designs and experiments, leading to the conclusion that while deep sleep consolidates memory, REM sleep has a role in helping the brain to form and find associations between distantly related concepts, images or ideas.
Sleep as therapy: Processing our emotions while slumbering.
Can sleep help us to process our emotions – and perhaps even to overcome trauma? Research has already established an overlap between the brain systems involved in some of the stages of sleep and the neuronal networks involved in emotional regulation.
In particular, during REM sleep, the emotional and memory encoding centres of our brains in the limbic system, as well as parts of the prefrontal cortex become active, while our motor systems are switched off (preventing us acting out our dreams). Scientists believe that this configuration allows the prefrontal cortex which is involved in planning and problem solving to work with the emotional and memory centres to process emotions and associated experiences into context and encode these into memory.
In an experiment to test this theory, an MRI scanner was used to measure brain activity, in a group of young adults who were shown a set of emotionally laden images twice, with a 12 hour interval in between. The participants were randomly split into two groups, one was shown the images before and after a night’s sleep and the other were shown the images in the morning and the evening of the same day, thus staying awake between the two viewings. Their brain scans showed that the group who slept between viewings, showed less emotional reactivity at the second viewing than the wakefulness group. Recordings of brain activity while they were asleep in the sleep laboratory clearly indicated an association between REM sleep and the reduction in emotional reactivity in this group. It appears that sleep – and in particular – dream sleep (REM) has helped these participants process the emotional material they were exposed to.
This type of laboratory research is complemented by findings from clinical research that shows that poor sleep is associated with almost all known mental health problems, from depression and anxiety to post-traumatic stress disorder. (And clinicians will recognise the significance of the return of good sleep for recovery from mental illness!) Studies also suggest that good sleep is associated with self-reported positive emotions in healthy populations.
Can sleeping more help you live longer?
Although direct links between sleep and longevity have not yet been established, there is an emerging body of evidence that shows the importance of good sleep in the longest living humans. Contemporary modelling of longevity has shown that only about 25% of how long we live is determined by our genes; the rest is determined by factors that include lifestyle choices, socio-economic factors and the natural environment. In one study of Chinese centenarians, more than half reported good sleep quality with more than 60% reporting that they slept more than 9 hours a day.
Similarly, research from Japan indicates that lifestyle factors conducive to longevity tend to co-occur in older people. For instance, in the Japanese village of Ogimi, Okinawa Japan which has the longest life expectancy in Japan and the highest rate of centenarians in that country, a lifestyle survey indicated that, among octogenarians, good sleep health was associated with a diet rich in fish and seaweed, regular exercise, and taking short naps rather than dozing off during the day. In comparison with the poor sleep health group, those who slept well were also more likely to be active members of senior citizens’ clubs.
Less than enough sleep in older adults, however, carries with it increased risks of poor physical health, forgetfulness, and increased accidents. Some research has also indicated the importance of inadequate sleep as a risk factor for dementia.
Not getting enough sleep: What are some of the costs?
There is clear evidence that not getting enough sleep can lead to all kinds of accidents. Particularly worrying is the increased risk of being involved in road traffic accidents due to sleepiness at the wheel. Findings from a large scale survey in the United States, indicate that the risk of being involved in a motor vehicle accident almost doubles when the driver had only 5-6 hours of sleep the previous night. With less than 4 hours sleep, risks increase more than 10-fold! Fatigue and sleep deprivation can also lead to accidents at work, reduced productivity and performance, and absenteeism.
Lack of sleep has also been shown to increase the risk for a range of physical health problems, including cardiovascular diseases, diabetes, as well as a wide range of mental health problems. In addition there is now a growing evidence base to suggest that addressing poor sleep through psychological interventions, can lead to improvements in depression and other mental health symptoms.
So, the evidence is compelling! Getting a good night’s sleep is vital for functioning well. With good sleep, we learn better, we perform better, we feel better, and we may even live longer! Conversely, poor sleep increases our risks of developing chronic diseases such as heart disease or diabetes, increases the risk of accidents, and may increase our vulnerability to mental health problems. Given the evidence, if you want to improve your life in 2019, getting more, better quality sleep seems to me to be a no-brainer!
How to sleep better: Some simple steps you can take.
There are many steps you can take to improve your sleep. I plan to devote a later post to provide more information on this topic. For now, here are four very basic things you can do today to get you started on improving your sleep:
1) Give yourself at least 8 hours per night of sleep opportunity. If you know that you have to get up at 7:15 in the morning, go to bed at the very latest at 11:15, allowing your body the opportunity to sleep for around 8 hours.
2) Go to bed at a fixed time every night. Some sleep scientists recommend that you set an alarm clock to your regular bedtime as a way to help you be more consistent. A regular bed time will help you adjust your circadian clock to more consistently reflect your lifestyle.
3) Make your environment sleep friendly, especially in the last 30-60 minutes before you want to go to sleep: Switch off all your screens, wind down by reading a book or listening to calm, relaxing music (if you struggle to sleep, try to find a relaxation or meditation exercise that suits you to do regularly at this time.) And try to switch off or dim any bright lighting in your home, especially bright, blue-toned daylight bulbs, substituting warmer (yellow) light or candles.
4) Make sure your bedroom is a little cooler than room temperature, as your core body temperature needs to drop by one or two degrees for you to be able to sleep.
As we approach the middle of January, the chances are that flagging motivation will lead to many a New Year’s Resolution being abandoned. Getting more, and better sleep, however, is so important to your health and well-being that it is certainly worth building and maintaining some of the good sleep habits mentioned here as well those I plan to share in the next two installments. And, if you believe that you have a more serious sleep problem, do talk to your GP about your insomnia. There is now a range of effective treatments available for most sleep problems.
If you want to find out more about sleep, how it works and how you can improve your sleep, watch this space. In recognition of the importance of good sleep, I am planning two more posts on this topic. Next time, I hope to share with you some of the fascinating neuroscience of sleep, and the final post is planned to focus on sleep problems and how they can be treated.
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