Sleep - Part 1

Facing the facts

“Early to bed and early to rise, makes a man healthy, wealthy, and wise…”

Benjamin Franklin

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Photo by Matthew Henry on Unsplash

Determinants of sleep health

On average, we spend one third of our lives asleep, so it makes sense that we should aim to optimise our sleep patterns and behaviour by maintaining healthy sleep habits. Sleep health is determined by a large number of factors, but one major component is sleep duration. The average adult requires anywhere from 7-9 hours of sleep per night, but the best indicator of adequate sleep duration is feeling refreshed upon waking. In addition to duration, the timing of sleep is also key to maintaining adequate sleep hygiene. Natural circadian rhythms encourage us to sleep at night, which is why shift workers or night workers often struggle to sleep compared to daytime, regular hour workers.

Regular schedules play an important role in maintaining sleep health. Those who sleep and wake at similar times for long periods of time tend to sleep better than those with a varied schedule and are less prone to developing sleep disorders such as narcolepsy, insomnia and sleep apnoea, or suffer with fragmented sleep. In short, ideally, we would go to sleep and wake at the same time each day, ensuring that we feel refreshed each morning, knowing that we suffered minimal disruption throughout the night. If only life was so simple...

So…How well do we actually sleep?

In the UK, we get approximately 6 hours and 20 minutes of sleep each night - less than the minimum guideline of between 7-9 hours. Sadly, this figure is also on a downwards trend, with less sleep becoming more common. As of 2022, only 6% of us meet the recommended guidelines for sleep duration, and that 6% of the population takes an average of 6 days less off work with illness in one year than the other 94%. Nearly 25% of people cite stress as the major cause for a lack of sleep, with 1 in 3 people experiencing a sleep disorder. It seems that there is a clear two-way relationship – the modern lifestyle is stressful, which causes us to sleep less, which leads to more stress, and the pattern continues.

Sleep and Health

So, if you’re reading this, there is a statistically high chance that you are one of the 94% of individuals who do not get enough sleep each night. If so, there is some more bad news. Whilst losing sleep for the short term can be overcome, over months and years, you are at elevated risk of mood swings and disorders, with 80% of poor sleepers reporting regular low mood. There is also a near 500% increase in the likelihood of you feeling lonely often. However, it is not just mental health which is impacted by poor sleep. If you achieve fewer than 6 hours per night, you are more likely to suffer a stroke, heart attack, or experience a form of a cardiovascular disease than those who sleep for at least 7 hours per night. Furthermore, your blood glucose regulation is impaired, meaning an elevated risk of developing diabetes. Immune function becomes suppressed, leaving you more vulnerable to bacterial and viral infections. Cognitive performance – memory, concentration, and reaction times are all decreased, as is your exercise performance. Moreover, there could be an increase in the likelihood of Alzheimer’s later in life. You may even be at higher risk of developing some cancers. Perhaps more immediately, poor sleepers tend to be more sensitive to pain. This then exacerbates the issue – higher sensitivity to pain can lead to even poorer sleep. Ultimately, unhealthy sleep patterns which occur regularly over long periods of time are linked to an increased risk of mortality and premature death. How do you know if you are a poor sleeper? You should be able to notice. Needing to take naps during the day is a sign of unhealthy overnight sleep patterns. You may feel groggy, irritable or have a reduced attention span in the day. You may also feel like your decision-making skills are impaired or that you can’t remember things as well as you should. If this seems familiar, then you may be one of the 94%.

Sleep Regulation

There are a few factors which determine how well we sleep, including: The body clock and circadian rhythm, sleep drive/ sleep pressure, and attitudes towards sleep.

Each person’s body clock is completely unique. In some ways, it is like a sleep fingerprint. The main driver of a body clock is the circadian rhythm. Our body is designed to respond to certain stimuli throughout the day, with the main stimulus being natural daylight. Just as nocturnal animals know to sleep during the night, diurnal beings like ourselves respond to daylight as their cue to wake up and stop sleeping. There is a specific part of the brain called the Suprachiasmatic Nucleus, or SCN, which is sensitive to changes in natural light levels, and it is this area of the brain which causes us to feel sleepier during the night-time and more alert during the day. Whether this is something you are consciously aware of or not, humans are designed to be productive when there is daylight, and the body is hardwired to make this happen. When the sun sets and natural daylight is replaced by darkness, the SCN sends signals around the body to increase levels of a hormone called Melatonin. Some people call this the Dracula hormone, because it increases in concentration at night. Melatonin makes us feel sleepy and encourages sleep processes during the night, with levels of the chemical at their highest in the early hours of the morning. Unfortunately, the body loves routine, and if our routines change, sleep is usually one of the first aspects which is impacted. An example of this would be when we go on holiday and enter a new time zone. Instead of having a solid routine, our body clock must adjust to the new sunrise and sunset schedule.. The further we travel, the more extreme this change is, and the longer it takes to adjust to the changes. ‘Jet lag’ is our brain’s way of adjusting to the difference in schedule and helping us to set suitable sleep and wake cues based on the new location. However, we don’t need to fly for 12 hours around the globe to suffer these effects. Shift workers will be all too familiar with the impact of work irregularity on sleep quality – more on this later.

Our circadian rhythm is extremely sensitive, but there are steps we can take to help it out. If possible, expose your eyes to natural sunlight as soon as possible after waking. This helps to kick start the process of reducing the levels of Melatonin in the body and should make us feel a bit less sleepy. Keeping a regular schedule also helps – those who can wake and sleep at similar times every night will notice a better sleep quality on average, than those who work shifts, or with very varied schedules. If changes in schedules are unavoidable, and there is some flexibility, then trying to change the schedule by 1 or 2 hours at a time as opposed to making one substantial change, as this will lessen the strain on the brain to accommodate these changes.

Another key component of sleep duration and quality is sleep pressure, or sleep drive. This simply describes how much the body needs to sleep. Imagine a balloon: the amount of air in the balloon represents sleep drive. When we are awake, the balloon slowly fills with air, getting bigger and bigger, expanding regularly throughout the day. The more air is in the balloon, the higher our sleep drive, and, in theory, the better we sleep at night. As we sleep, the balloon deflates, and after a full 7-9 hours of good quality sleep, the balloon is completely empty once more, ready to be inflated the following day. Whilst simply being awake will fill the balloon eventually, it will not do so very quickly, and we might have to be awake for 17 hours or more to fill the balloon this way. Exercising in the daytime will accelerate the inflation of this balloon, increasing sleep drive.

A Passive Process…

Sleep is not an active process. When we fall asleep, by definition, we are switching off and not thinking. Trying to force yourself to sleep very rarely works, but the opposite is very much true. The old method of counting sheep is a task designed to try to keep the individual’s attention span on one specific task, and to distract them from trying to actively fall sleep. It has often been said that sleep will only come once you ignore it. How many people will listen to an audiobook in bed, or fall asleep in front of the TV? The act of trying to pay attention to a storyline so often leads to sleep.

So, you finally nod off….what happens next?

Stages of sleep

There are 5 sleep stages, including being awake, which progress from light sleep to deep sleep.

• N1) This is light sleep. This stage typically lasts up to 5 minutes and it is fairly easy to wake someone in this period.

• N2) Lasts up to 60 minutes and is slightly deeper than N1. During this time, body temperature and heart rate drop. Memories are consolidated during this phase of sleep, and due to the fact that it appears twice in each sleep cycle, the majority (up to 45%) of sleep is N2 sleep.

• N3) Also known as slow wave sleep, delta sleep, or deepest non-REM sleep. This typically lasts 20-40 minutes and accounts for roughly 25% of the sleep cycle. Being woken in this stage will lead to confusion and grogginess, and cognitive performance can be impaired for up to an hour after being woken during this stage. Tissue repair and immune system optimisation occur during this phase, whilst bed-wetting and sleep walking also occur in N3 sleep.

• REM Sleep) Lasts 10-60 minutes and accounts for 25% of sleep. This is the stage where dreaming and nightmares take place, and the skeletal muscles do not move. The eyes remain active and rapidly move, giving this stage its name.  

A sleep cycle is an average of a 90 minute block of sleep, where the stages of sleep occur in the following order: N1, N2, N3, N2, REM. There may be 4-5 sleep cycles each night depending on length of sleep and other factors.

So - we now understand what sleep is, the different stages, and how important it is to have an optimised sleep routine. Statistically, you, the reader, don’t sleep healthily enough, so what can you do? This will be revealed in part 2 - see you there.