How to Sleep Well: The Science of Sleeping Smarter, Living Better and Being Productive by Neil Stanley (Notes)
Slow Wave Sleep (SWS), plays a crucial role in our capacity to deal with the events of the day, to lay down memories, and to learn new tasks.
As the Rev. Dr Wills wrote in 1864 ‘Those who think most, who do most brain work, require most sleep’
Sleep is divided into two distinct states, Rapid Eye Movement (REM) sleep and non‐REM sleep, with non‐REM sleep being further divided into three stages; N1, N2, N3, each of increasing depth. During the night you pass through the four sleep stages: N1, N2, N3, and REM sleep in what are known as ‘sleep cycles’. Sleep progresses cyclically from N1 through to REM, then begins again with stage N1. Each sleep cycle lasts approximately 90 to 110 minutes in adults. The first couple of sleep cycles have long periods of uninterrupted deep N3, or Slow Wave Sleep (SWS), with relatively short REM periods. Later in the night the REM periods lengthen and SWS is mostly absent. Thus, the first third of the night is predominantly SWS sleep and the later part of the night is spent in the lighter stages, N1, N2, and REM sleep.
Stage N1 (3–7% of sleep) is the lightest stage of sleep and is the transition between wake and sleep. It is the type of sleep that you have at the start of the night when you feel you are drifting in and out of sleep. When you are in stage N1 sleep you can be woken easily, and indeed if you are awakened you will probably claim not to have been asleep. During the transition from wake to sleep, many people experience sudden muscle contractions or ‘jerks’; a sensation of falling or a ‘presence’, benign or otherwise, in the room. There are a number of complex processes that need to occur, and these so‐called hypnagogic events seem to be ‘glitches’ in the preparation for sleep. Although they may be perceived as worrying or scary they are in fact normal and harmless. N1 is also the sleep stage you are in when you are dipping in and out of when you wake in the middle of the night and feel you have been awake for hours.
Stage N2 accounts for 45–50% of sleep and, although it is the biggest single portion of sleep, it is the stage which we know least about. It is known to play a part in memory but as yet we do not completely understand why we spend half the night in this stage.
As sleep becomes deeper, slow brain waves (called delta waves) start to appear and we enter N3 or SWS (20–25% of sleep). N3 is the deepest stage of sleep and when someone is in SWS it can be very difficult to wake them. SWS is believed to be most closely linked with the restorative processes of sleep and is thus the part of sleep that makes you feel like you have had a good sleep. It also plays a key role in making you feel well rested and energetic during the day. SWS is important for memory and learning and it is for this reason that children have proportionally more SWS than adults, as well as the fact that SWS is the only time that you physically grow. It is during SWS that some people, particularly children, experience behaviours (known as parasomnias) such as bedwetting, sleep talking, sleepwalking or night terrors. Both short and long sleepers essentially have the same amount of SWS thus it seems as though a minimum amount of N3 deep sleep is needed per night, no matter how long the total sleep time. Given the importance of SWS after partial or total sleep deprivation the brain attempts to make up all the missed SWS.
During Rapid Eye Movement (REM) sleep (20–25% of sleep) the eyes can be observed jerking rapidly back and forth under closed eye lids, hence its name. It is during REM sleep that most of our ‘story‐like’ dreams occur (dream‐like events can occur in any stage of sleep but they are generally thought to be shorter, more focused on a single emotion and lacking the narrative complexity of dreams in REM sleep). REM sleep is involved in processing emotional memories and ensuring our psychological health. During REM our brainwave activity can increase to levels experienced when a person is awake, breathing becomes more rapid, irregular and shallow, heart rate increases and blood pressure rises. In order that we do not act out our dreams we lose muscle tone during REM and thus we are effectively paralysed.
However, good sleep is both quantity and quality i.e. it is important to get the right proportion and distribution of the various sleep stages during the night. Additionally, your sleep should as far as possible be unbroken and of the correct duration for you.
Our sleep is regulated by two body systems: sleep/wake homeostasis and our circadian rhythm (aka ‘body clock’). Sleep/wake homeostasis essentially tells us how long we have been awake and, at the end of the day, tells us that it is time to go to sleep. Our circadian rhythm regulates our sleepiness and wakefulness over a 24‐hour period. The circadian rhythm rises and falls across the day with our strongest drive to sleep generally occurring between 2–4 a.m.. We also have another much weaker desire for sleep during the afternoon between roughly 1–3 p.m., the so called ‘post‐lunch dip’ which, because it is a function of our circadian rhythm, does not actually need food for it to occur. Our individual circadian rhythm dictates whether we are a ‘morning person’ or an ‘evening person’ as well as the exact timing of our individual peaks and troughs of alertness and sleepiness across the 24 hours.
The most important signal that it is time to go to sleep is darkness, in response to which the brain produces a hormone called melatonin. The release of melatonin is the signal that initiates a number of processes that lead us to fall asleep. Melatonin levels drop across the night and in the morning approximately 90 minutes prior to our wake‐up time our body clock starts a series of changes (e.g. increase in body temperature, production of the hormone cortisol) that results in our awaking. This is why you have an ‘uncanny’ ability to wake up before your alarm goes off. If the body knows when you are going to wake, because you have set the alarm, or because (as recommended) you have a regular wake‐up time, it can actually prepare to wake up naturally at that time (as long as you are not severely sleep deprived). However, if the body does not know when you intend to wake it cannot prepare and thus you are liable to feel groggy when you wake.
The major external stimulus that signals the fact that it is day is sunlight and it only takes a few minutes of daylight to tell our brain that it is time to be awake. Even through closed eyes sunlight can signal that it is time to wake up, hence why in summer we often wake early. Because of our dependency on light and dark to entrain our body clock our sleep need varies with the seasons. In summer we have a natural tendency to sleep less and in winter, when it is dark and cold, we tend to want to sleep more.
Individual sleep need is like height – we are all different and it is, to a large degree, genetically determined. Anywhere between four and eleven hours can be considered normal
Your personal sleep need is essentially the amount of sleep that allows you to feel awake, alert, and refreshed during the following day. Very simply, if you feel sleepy during the day then you are probably not, for whatever reason, getting the sleep you need during the night.
eight hours is not the recommended length of sleep, and actually never has been. It is disingenuous to suggest that eight hours sleep is anything other than an average, it is not an ideal.
In the past various writers commented on the number of hours sleep needed, for instance Bullein in 1576 states that
‘sixe or eight houres will suffice nature’.
Vaughan in his Naturall and artificial directions for health (1600) writes
‘How many houres may a man sleepe? Seaven houres sleepe is sufficient for sanguine & cholerick men; and nine houres for fleagmaticke, and melancholick men.’
And the book Directions and Observations relative to Food, Exercise and Sleep (1772) states
‘It is not possible to lay down any Rule as to the Length of Time necessary for Sleeping; for as this does in a great Measure depend upon Age, Habit and other Circumstances, it ought in different Persons to be different: But it seems to be agreed, that it ought not in the general to be less than six nor more than nine Hours in a Day.’
This advice is confirmed by seventeenth to nineteenth century proverbs that variously say
‘The Student sleepes six Howres, the Traueller seven; the Workeman eight, and all Laizie Bodies sleepe nine houres and more.’
‘Nature requires five, Custom gives seven! Laziness takes nine, And Wickedness eleven.’
‘Six hours for a man, seven for a woman, and eight for a fool.’
The National Sleep Foundation consensus statement is often quoted seven to nine hours; however, the recommendations define times as either as ‘recommended; may be appropriate for some individuals; or not recommended’. There is no clear explanation of ‘some individuals’, so it is perhaps clearer to quote the durations of sleep that are ‘not recommended’ which for adults (26–64 years) is less than six hours sleep or more than ten hours sleep.
Although the timing of our sleep can be dictated by such external factors as our jobs, lifestyle, and so on, morningness (aka ‘lark’) and eveningness (aka ‘owl’) are to a large part genetically determined.
(For a more scientifically valid way to measure whether you are a lark or an owl search for a copy of the Horne and Ostberg morningness and eveningness questionnaire.)
Because of the genetic predisposition it is not possible for you to ‘train’ yourself to become a lark or owl. All that you can really do is learn to how cope with the effects of being out of phase and to reduce the impact. For instance, owls would benefit from getting exposure to daylight as soon as possible after they wake up. Larks may find that getting out in the daylight late afternoon/early evening helps them to stay awake longer. The impact of morningness/eveningness is most acutely observed in owls who because of societal pressures often need to wake up much earlier than their natural propensity to wake, this causes them to experience ‘sleep inertia’, that feeling of grogginess in the morning that can persist for between 15 minutes and 2 hours after waking.
Sleepy means a propensity to go to sleep, tired implies physical and/or mental fatigue/exhaustion. Therefore, you can be tired without being sleepy
‘One hour's sleep before midnight is worth two after’. (The earliest source, from 1640, gives the idea that one hour's sleep before midnight is worth three after; but from 1670 the proverb equates its worth to two hours). This proverb is simply explained by the fact that deep SWS is predominant in the first third of the night and so much of the restorative benefit of sleep is achieved in that period. Thus, given a bed time of 9 or 10 p.m. a person gets most deep restful sleep in the hours before midnight with lighter and less refreshing sleep in the hours after midnight. So, it has nothing to do with ‘midnight’ per se and more to do with the timing of deep restorative sleep being in the first third of the night, whenever this occurs. This proverb is now only used as a way of trying to persuade your teenage daughter to come home at a reasonable time.
While research shows it can take up to three days for your internal body clock to ‘reset’ when the clocks change, it is not ‘incredibly disruptive’.
The best advice for helping your body deal with the time change is to make sure you change all your clocks to the new time before you go to sleep, meaning that you hit the ground running when you wake up.
Don't overthink ‘losing’ or ‘gaining’ an hour – if you normally wake up at 7 a.m., then get up at 7 a.m. rather than trying to overcompensate for the change in time. And most importantly don't hit snooze! Routine is key to good sleep.
A dream is a subconscious experience of a sequence of images, sounds, ideas, emotions, or other sensations occurring predominantly during REM sleep. Everyone dreams four or five times a night, but you can only remember a dream if you wake up during it or within a couple of minutes of it finishing. If you do not remember your dreams, it is probably that you are just a good sleeper, hence you are not waking up during your dreams. Conversely, if you feel you are always dreaming it probably means that your sleep is being frequently disturbed for one reason or another.
When we are dreaming, the dream is, for all intents and purposes, real to both our mind and body and so the body can have a physiological response to what occurs in the dream. We have all woken from a dream with our heart pounding, feeling out of breath, sweating, and feeling a sense of fear or anxiety.
when we dream we lose muscle tone. We are thus unable to act out our dreams. Essentially, we become floppy, except interestingly a part of the male anatomy that frequently does the exact opposite. However, this has nothing to do with the content of the dream and everything to do with simple fluid dynamics. Sexual dreams in fact only occur about 10% of the time although erections occur in approximately 80% of dreams.
The actual content of our dreams is limited in certain ways. When we are asleep we are at our most vulnerable and therefore we still need to remain vigilant to what is going on in the environment. However, as our dreams are essentially real experiencing certain sensations in our dreams would compromise our vigilance, which could have serious consequences. For instance, because the sleeper is unable to see or move when asleep, vision and movement do not play a role in providing accurate information about the external world and therefore they can exist in our dreams without compromising vigilance. This is why the overwhelming majority of our dreams are visual and we can experience motion, such as the common feeling of flying. However, because we have to rely on our other senses to provide information about what is going on, sensations such as touch, smell or certain sounds, that would compromise vigilance by interfering with signals coming from the external environment, rarely occur in our dreams.
Anxiety is the most common emotion experienced while dreaming. As in the waking state, it has been found that men generally have more aggressive feelings in their dreams than women, while children's dreams do not contain much aggression until they become teenagers.
The only difference between your dreams and waking reality is that your dreams are internally generated. The content of your dreams can be made up of pretty much anything you know or can imagine. Time is compressed or distorted in your dreams. Your dreams start out as a jumble of images etc. which your brain's tries very hard to make sense of. So, however weird and abstract your dreams seem, they are in fact the best interpretation your brain can make of what is going on in your mind. Your dreams only become the stories you think they are when you tell them to your partner/therapist.
If your dreams are so important and meaningful why do you have no memory of the vast majority of dreams that you have and only partial memory of those that you think you do remember? What are these ‘forgotten’ dreams telling you, and how do you know?
Dreams have as much or as little meaning as you would like to invest in them. Beethoven dreamed symphonies; I will never dream symphonies because I am completely non‐musical. You don't need people or dream interpretation books to understand what your dreams mean. Essentially that is like asking someone to tell you what you think. Look for the meaning within yourself because your dreams are part of you.
Lucid Dreaming: It's a Gateway to Creativity, Man
Proponents of lucid dreaming make outlandish claims as to their ability to explore new realms of consciousness and creativity while controlling their dreams. In a lucid dream the dreamer realises that they are simultaneously conscious and dreaming, therefore they are able to make decisions concerning their dream, or directing it in some way. The art of lucid dreaming is having the conscious awareness that you are dreaming without, by doing this, causing yourself to wake up.
Lucid dreaming is a bit like anything, some people find it easy while others will wake up every time they try to do it. Given the fact that any dream can only be made up of things you know or have experienced, and given the fact that in order to lucid dream you are using your conscious mind, it cannot be a gateway to a new realm of consciousness.
There is no ‘normal’ or ‘right’ amount of sleep for a child, only broad recommendations. The National Sleep Foundation recommends the following sleep durations, per 24 hours:
| New‐borns | 0–3 months | 11–19 hours |
| Infants | 4–11 month | 10–18 hours |
| Toddlers | 1–2 years | 9–16 hours |
| Pre‐schoolers | 3–5 years | 8–14 hours |
| School‐aged children | 6–13 years | 7–12 hours |
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