Quality sleep, getting enough of it and at the right times, is as essential to survival as food and water. Before the 1950s, most people believed sleep was a passive activity during which your body and brain were dormant. But it turns out that sleep is a period during which your brain is engaged in a number of activities necessary to life, and closely linked to the quality of it.
You spend about one-third of your life sleeping, and it's during sleep when your nervous system rests, your brain detoxifies, your memories are stored and your body heals. Without it, you can’t form or maintain the pathways in your brain that let you learn and create new memories, and it’s harder to concentrate and respond quickly.
What is sleep?
When you close your eyes, your brain’s activity changes. You cycle through a number of sleep stages, an average of four to five times a night with each loop taking progressively longer.
Each stage is characterised by different electrical activity. Neurons in your brain start firing in synchrony, your heart rate, breathing rate and brain activity gradually slow down and you enter REM (rapid eye movement) sleep.
Throughout your time asleep, your brain will cycle repeatedly through two different types of sleep: REM sleep and non-REM sleep. Each stage of sleep is linked to specific brain waves and neuronal activity, which change as you cycle through the stages.
Stage 1: Non-REM sleep is the transition from wakefulness to sleep. During this short period of fairly light sleep (lasting only a few minutes) your heartbeat, breathing, and eye movements slow down, and your muscles relax with occasional twitches. Your brain waves begin to slow from their daytime wakefulness patterns.
Stage 2: Non-REM sleep is a period of light sleep before you enter deeper sleep. Your heartbeat and breathing continue to slow down and your muscles relax even further. Your body temperature drops and eye movements stop. You spend more of your repeated sleep cycles in stage 2 sleep than in other sleep stages.
This light sleep clears your hippocampus (the part of your brain that plays a major role in learning and memory) to make room for new information the following day. After being awake for 16 hours, and taking in a lot of information during the day, it's difficult for your hippocampus to hold on to new information. Light sleep is like a refresh that renews your ability to learn new facts. Most of your light sleep occurs at the end of a full night’s sleep.
Stage 3 & 4: Non-REM sleep is your restorative sleep. It’s the period of deep sleep that you need to feel refreshed in the morning and occurs in longer periods during the first half of the night. Your heartbeat and breathing slow to their lowest levels during sleep and your blood pressure drops. Your muscles are relaxed and brain waves become even slower. It's during this stage when your body promotes muscle growth and repair and your brain detoxifies and flushes toxins through your glymphatic system. It may be difficult to awaken you during this stage, and if you do awaken, you may feel groggy and disoriented.
Why is REM sleep important?
During the day, your hippocampus temporarily stores information, like names or the steps of a new work procedure. During deep sleep, your mind transports this data from the hippocampus to permanent storage in your long-term memory. If you decide to stay up late and skip out on the first two hours of your regular sleep schedule, you’ll miss most of your deep sleep and fail to store important information in your long‐term memory.
REM sleep first occurs about 90 minutes after falling asleep. Your eyes move rapidly from side to side behind closed eyelids, Your breathing becomes faster and irregular, and your heart rate and blood pressure increase to near waking levels. Most of your dreaming occurs during REM sleep, although some can also occur in non-REM sleep. Your arm and leg muscles become temporarily paralysed, which prevents you from acting out your dreams. As you age, you sleep less of your time in REM sleep.
When you enter REM sleep, your mind begins to make sense of what happened during the day by connecting newly stored information with previously stored information. The connections can often be bizarre, which are usually seen through vivid dreams, and can often lead to creative breakthroughs. You benefit from memory, learning and problem solving during this stage. REM sleep not only provides creative insights, it offers emotional insights too.
In summary, light sleep improves your ability to learn new information, deep sleep improves your ability to recall information, and REM sleep improves your ability to make sense of information, and any related emotion.
Everyone dreams. We spend about two hours each night dreaming, although some people may not remember them.
The exact purpose of dreams isn’t known, but it's thought that they may help us to process our emotions. Events from the day often override our thoughts during sleep, and people suffering from stress or anxiety are more likely to have frightening dreams or nightmares. Some people dream in colour, while others only recall dreams in black and white.
What is sleep controlled by?
Cells in your brain and body follow an internal master clock: your circadian rhythm. With each rotation of the sun around the earth, light intake and your feeding behaviour resets your circadian rhythm to Earth’s 24 hour day. Daily reset is vital for health and survival.
Each cell in your body has a clock. Light passes through the retina of your eyes and into the master clock, which is located in part of your brain called the suprachiasmatic nucleus, or SCN. This brain region, found in the hypothalamus, coordinates a complex hormonal circuit which sends signals and information to organs, muscles and tissues, synchronising your body with the time of day and helping promote sleep onset.
These signals vary throughout the day. At night, your SCN receives signals that it’s dark and late in the day. This causes it to send a message to the pineal gland in the brain that it’s time to release melatonin, which makes you sleepy. The opposite occurs during the daytime because light signals suppress melatonin production.
How well you sleep and eat in synchrony with night and day determines the healthy or disordered production of hormones that change your behaviour. These include hormones responsible for stress, appetite, sleepiness and insulin control. It’s common to feel energy dips throughout the day, and these dips can vary based on your individual habits and age.
Sleep drive also plays a key role. Your body craves sleep just as it craves food when you're hungry. Throughout the day, your desire for sleep builds, and when it reaches a certain point, you need to sleep. A major difference between sleep and hunger is that your body can’t force you to eat when we’re hungry, but when you're tired, it can put you to sleep. When you're exhausted, your body is even able to engage in microsleep episodes of one or two seconds while your eyes are open. Napping for more than 30 minutes later in the day can throw off your night’s sleep by decreasing your body’s sleep drive.
Benefits of sleep
Everyone needs sleep, but its biological purpose is still not fully understood. We know that sleep is important to a number of brain functions, including “brain plasticity”, or how nerve cells communicate with each other. If you sleep too little, you become unable to process what you've learned during the day and you have more trouble remembering it in the future.
Sleep also helps to “clear the mind” by promoting the removal of waste products and toxins in your brain that build up while you're awake. This occurs through the glymphatic system.
Sleep is vital to the rest of your body too. It affects almost every type of tissue and system in your body, from the brain, heart, and lungs to metabolism, immune function, mood, and disease resistance. A chronic lack of sleep, or getting poor quality sleep, increases the risk of certain disorders, causes your immunity to become compromised and can create a prediabetic state in an otherwise healthy person.
How much sleep do we need?
How much sleep you need depends on your age. For adults, the recommendation is 7-9 hours. Babies initially sleep as much as 16 to 18 hours per day, which may boost growth and development (especially of the brain). School-age children and teens need between 9-11 hours of sleep per night.
In general, people are getting less sleep these days than they need due to longer work hours and the availability of round-the-clock entertainment and other activities. Many people feel they can "catch up" on missed sleep during the weekend but, depending on how sleep-deprived they are, sleeping longer on the weekends may not be adequate.
Ways to sleep better
From the moment you open your eyes you can influence better sleep habits to teach your body when it’s bedtime and enhance the quality of the sleep you have.
Stick to a consistent sleep schedule
Setting a regular bedtime and wake time each day, and sticking to it, is one of the best ways to keep your circadian rhythm balanced. As tempting as it can be to sleep in on weekends, this can throw off your body clock during the week.
Get natural sunlight
Exposing yourself to natural light in the day does more than just boost your energy, it also helps you sleep better at night. Melatonin production is reduced when you're exposed to light, so getting outside, ideally in the sun, for a 20 minute stroll first thing in the morning is one of the most powerful ways to regulate your circadian rhythm and tell your brain it’s time to start the day. If you can’t get outside, open your blinds and look into the sky for 30 seconds, or switch on a bright light. Melatonin release works like an elastic band, the more you suppress it by getting outside in the day, the more it rises in the dark to promote sleep.
Reduce exposure to artificial light
Overexposure to bright light, in particular electric and artificial blue lighting (the type that laptops, tablets and mobile phones emit) late at night disrupts the secretion of melatonin levels, tricking your brain into thinking it's still daytime and making you feel less tired. Dim your lights or use candles when the sun goes down, and set your screens to “night mode” or “twilight” a few hours before bed. Ideally, switch off screens one hour before bed and turn your phone onto aeroplane mode when you go to bed.
Use relaxation practises
Having an evening relaxation practice such as meditation, mindfulness or a breathing exercise can help you get into a state of relaxation. This will not only help you fall into a deep sleep, but it can also help reduce stress and quieten the thoughts and emotions you've built up throughout the day. You can also try calming essential oils such as lavender, chamomile or ylang ylang.
Your body temperature needs to drop 2-3 degrees to initiate sleep, and heat can trigger wakefulness and decrease important slow-wave and REM sleep stages. Try to keep your bedroom cool to ensure you rest easier.
Avoid going to bed too full or too hungry
The timing of when you eat may have a significant effect on sleep patterns. Eating large portions in the evening, close to bedtime, may result in disruptions to healthy sleep patterns. Aim to finish your evening meal 2-3 hours before going to bed. If you do need a snack before bed, carbohydrate-rich foods like whole wheat toast, bananas or oatmeal can help to trigger the release of the sleepy hormone serotonin, and they don’t take long to digest.
Time your workout
Cortisol is produced in response to high intensity exercise. If you're having trouble sleeping, it may be a good idea to schedule higher intensity exercise in the morning or early afternoon to work with your natural cortisol curve. If you do want to do some gentle movement in the evenings, stick to yoga, Pilates or a light stroll. An added bonus, more mindful movement can incorporate breath work and meditation which can help promote relaxation, right before bedtime.
There are many nutrients that can help to promote good sleep. Foods rich in the amino acid tryptophan can help boost the production of the sleep-inducing melatonin hormone. Chicken, turkey, eggs, cheese, yogurt, and nuts and seeds are all good choices. Combining these foods with rice, pasta or potatoes for your evening meal can help your body get the most benefits from tryptophan and aid sleep. Tart cherries contain a natural source of melatonin, so sipping a glass before bed can be beneficial for sleep.
Sleep is a crucial part of health and healing. Having a healthy circadian rhythm starts from the minute you wake up, so stay away from stimulants and focus on implementing some healthy sleep practices to ensure you get the best restorative sleep for a healthy mind and body.