As recently as 70 years ago, researchers assumed the human body went into a dormant state during sleep. It was thought that the body and mind became inactive during sleep to rest and recover from the day’s activity. However, we now know that quality sleep is a complicated, dynamic physiological process that is anything but passive. Our body and mind work to restore, regenerate and process information during sleep so that we can function optimally in daily life.
Keep reading to learn about the different stages of sleep, why deep sleep is important and how you can get more of it.
What is Deep Sleep?
When we sleep, we go through several sleep cycles about every 80 to 110 minutes, each of which is made up of four phases. Phases one to three are called NREM (non-rapid eye movement) sleep, while phase four is the well-known REM (rapid eye movement) sleep.
Scientists discovered the different sleep phases by measuring changes in the electrical activity of the brain during sleep using an electroencephalogram (EEG).
When we are in a regular waking state, we experience Beta brain waves of 14-30 Hz. If we are awake but highly relaxed, our brain waves slow down to an Alpha state between 9-12 Hz.
Our sleep cycle begins with phases one and two, which are stages of light sleep where our brain waves slow down and transition from an Alpha to a Theta wave state of 4-8 Hz. Our heart rate and breathing slow down, muscles relax and body temperature drops. It’s relatively easy to be woken during these phases.
The third phase of NREM sleep is deep sleep - this was previously split into two separate phases but scientists have since condensed it into one. When we are in deep sleep our blood pressure and heart rate drop and muscles let go completely. The thinking mind becomes relaxed and we do not dream. In this state, our brain waves slow down to 1-3 Hz as we enter into a predominantly delta wave state where we are unlikely to be woken up or disrupted. If we are woken during deep sleep, we can experience sleep inertia which results in confusion, fatigue, grogginess and poor mental performance (1).
Interestingly, we experience most of our deep sleep during the earlier part of the night, and this phase becomes shorter as we move through sleep cycles.
During deep sleep, the pituitary gland in the brain secretes human growth hormone (HGH), which is responsible for repairing and regenerating our energy, cells, neurons, bones, muscles and immune system.
REM sleep is the phase that follows deep sleep and is named because our eyes move quickly from side to side during this phase. During REM sleep, we return to a lighter sleep state where the brain waves speed up and may look similar to those of someone who is awake. In this phase, our heart rate and breathing also speed up, and we experience dreaming. There is a lot of talk and research around REM sleep because it is our dreaming state, but generally less is known about deep sleep. In fact, many people incorrectly believe that REM sleep is a state of deep sleep.
Although there is no set requirement for deep sleep, it’s estimated that adults spend about 13-23% of total sleep time in this phase. Children and adolescents need more time in deep sleep — and sleep in general — due to its important role in growth.
The Importance of Deep Sleep
Even though there is less said about this phase, it is an incredibly important part of sleep that we enter several times per night. Deep sleep is responsible for restoring and regenerating the body and brain and allows us to feel refreshed and rested when we wake up in the morning.
Getting enough deep sleep encourages the growth and repair of muscle tissue, which is beneficial for those doing weight training and trying to build muscle. Besides the release of HGH, blood flow to the muscles increases during deep sleep.
In addition to restoring the body, we are now finding out deep sleep may also have a significant benefit to the brain. Animal studies have shown that slow-wave NREM sleep is the optimal time for the brain to remove waste and cleanse itself (2). Unfortunately, people who aren't getting enough deep sleep may have less efficient waste removal in the brain which will lead to the accumulation of toxic proteins and plaques. So, getting poor quality sleep could be a major risk factor for Alzheimer's disease.
Deep sleep is not just important when it comes to cleansing the brain; it also helps us to learn! Deep sleep is vital for the brain to refresh, recover and allow for learning. One study found that when human test subjects didn't get deep sleep, their ability to learn and perform different finger movement sequences was negatively impacted (3). This makes sense — none of us feel capable of learning or focusing on anything after a poor night’s sleep!
Are You Getting Enough Deep Sleep?
Getting enough quality sleep each night — which includes the stage of deep sleep — is important to overall health and well being. Unfortunately, research shows that as much as 45% of the world’s population is consistently not getting enough sleep (4).
The best way to tell if you are getting enough deep sleep is to gauge how you feel when you wake up and notice your energy levels and sleepiness throughout the day.
Are you woken up frequently throughout the night? Are you getting less than 6 hours of sleep per night? Do you wake up in the morning feeling groggy and unrefreshed? Do you need to take naps during the day or easily fall asleep at school or work? Do you find yourself feeling sleepy and can barely keep your eyes open when evening arrives?
If you answered yes to one or more of those questions then the chances are that you’re not getting enough deep sleep.
Other issues that can be detrimental to getting deep sleep include having young children, chronic stress, pain, working night shifts, ageing, certain pharmaceutical drugs and sleep disorders like sleep apnea.
Getting at least 15% is deep sleep is sufficient, but aiming for 20% is optimal.
A wearable device such as the Orua Ring measures your movement, heart rate and sleep habits may help you to identify how much deep sleep you get each night.
How To Improve Deep Sleep
If you’ve identified yourself as someone who does NOT get enough deep sleep, you’re probably wondering how to get more of this restorative and energizing state.
We’ve compiled 15 simple tips to help you improve your chances of getting enough quality deep sleep.
1. Focus on Sleep Hygiene
Luckily, getting more quality deep sleep is possible and within our reach. The most important tip is to work on improving overall sleep and this starts with good habits leading up to bedtime — known as sleep hygiene. You can read more about sleep hygiene and how to implement it in our article “What is Sleep Hygiene and 9 Simple Tips to Improve It”.
2. Give Yourself Enough Time
The shorter our sleep duration is, the less chance we have of cycling through all the stages of sleep and spending enough time in each stage.
You are more likely to get enough deep sleep if you give yourself sufficient time to wind down, fall asleep and sleep without interruption. Set yourself a regular bedtime and wake up time which allows you enough time to get the recommended 7-8 hours of quality sleep each night.
3. Say No to Long Naps
Taking long naps during the day may result in reaching the deep-sleep phase. This will decrease what is known as your “sleep drive”, resulting in feeling less sleepy in the evening and making falling asleep when you need to more difficult. If you need to nap during the day, short naps of about 20-30 minutes should allow you to stay in the lighter sleep phases one and two (5). This will help to boost energy and brain function while avoiding falling into a deep sleep.
4. Exercise
Getting active and expending energy by exercising during the early part of the day is incredibly beneficial to sleep quality.
Research suggests that light to moderate exercise — both aerobic exercise like cycling and jogging and anaerobic exercise like weight lifting — can improve sleep by reducing the time it takes to fall asleep as well as the number of times we wake during the night. Frequent exercise has also been linked to more time spent in deep, slow-wave sleep (6).
You can improve your sleep as well as your overall health by doing just 30 minutes of moderate intensity exercise each day. However, exercising within a few hours of bedtime as well as high-intensity exercise may have detrimental effects on sleep.
5. Block Blue Light at Night
Our internal body clock, known as the circadian rhythm, needs to be regulated to achieve optimal sleep. To carefully maintain this sleep-wake cycle and prepare us for sleep, the pineal gland in the brain produces a hormone called melatonin which is largely released in the evening in response to fading light. In the morning, when the sun rises, our body recognises an increase in light and melatonin production decreases. However, our use of artificial lighting and electronic devices in the evening exposes us to the blue light spectrum which can confuse the body into thinking it’s daytime.
To ensure that we are getting good quality sleep, we must decrease our exposure to blue light in the evening.
Studies have shown that wearing blue light blocking glasses when using a computer, tablet, kindle, gaming device and smartphone in the evening can improve sleep (11). Wearing these glasses is a simple and effective way to get better sleep quality, especially for those who work or study in the evening.
There are a few other simple ways to block blue light at night and improve sleep.
- Limit your use of TV and other electronic devices in the 1-2 hours before going to bed.
- Replace your regular light bulbs with red and orange bulbs to eliminate your exposure to blue light at night.
- Install blue light blocking software onto your computer and smartphone.
- Use blackout curtains in the bedroom to block out any ambient light coming from outside.
6. Increase Magnesium
Magnesium is a wonderful mineral that’s involved in a variety of important functions in the body. Its role in nervous system regulation, stress reduction, muscle relaxation and melatonin production make it a key mineral for improving sleep quality.
Increasing magnesium intake may be particularly useful for older people because our ability to reach deep sleep diminishes as we age. A study on elderly people with insomnia found that supplementing with magnesium improved their ability to fall asleep and stay asleep as well as their total sleep time. It also significantly increased the production of the sleep hormone melatonin and reduced levels of the stress hormone cortisol (7).
Improve your sleep and get more deep sleep by eating magnesium-rich foods such as whole grains, legumes, green leafy vegetables, nuts, seeds and fish. You can optimise your magnesium levels by taking a good quality magnesium supplement such as Life Extensions Neuro-Mag and soaking in a magnesium salt bath before bed.
7. Steer Clear of Big Meals before Bed
Having a small snack before bed can help to balance blood sugar levels and encourage sleep, but eating a large meal within 1-2 hours of bedtime can have the opposite effect.
A large meal before bed may disrupt sleep as energy is directed to digestion instead of the important reparative and restorative functions of sleep. It may also lead to uncomfortable digestive symptoms like acid reflux and cramps, not conducive to a good night’s sleep.
Eating a big meal before bed not only impacts our ability to fall asleep but can also affect the benefits of deep sleep by reducing the amount of human growth hormone (HGH) we produce. Unfortunately, insulin — the hormone released after eating a meal rich in carbohydrates — is an antagonist to HGH and can hamper our HGH production during deep sleep (8).
8. Avoid a Full Bladder
A full bladder during the night is likely to rouse you from sleep and may result in difficulty going back to sleep and getting insufficient deep sleep. Make sure to empty your bladder before attempting to fall asleep and avoid drinking liquids within 1-2 hours of bedtime.
9. Reduce Stress
Mental and emotional stress can hinder our ability to fall asleep at night. Stress triggers our flight or fight response which results in the release of stress hormones like cortisol that have a massive knock-on effect in our body. Instead of drifting off to sleep, we’re left lying awake for hours running worst-case scenarios through our mind or wakening several times in a panic.
Luckily, mind-body stress reduction techniques have been found to be a successful tool for people with difficulty sleeping (9).
Improve sleep quality by learning to manage your day to day stress with self-care techniques like deep breathing, meditation, calming music, walking, journaling, warm baths, aromatherapy and talk therapy.
As mentioned earlier, taking a magnesium supplement can benefit sleep by regulating the sympathetic and parasympathetic nervous system, reducing the effects of stress (10).
10. Get Rid of Distractions
Minimizing the amount of time that you wake up during the night will help ensure that you are cycling through each phase of sleep and spending enough time in deep sleep. Therefore, it’s important to identify and eliminate anything that could be causing sleep disruptions.
Invest in earplugs to block out excess noise, turn your phone off at night, put up blackout curtains to reduce unnecessary light from the environment and try to keep your room at a consistent temperature. Unfortunately, pets need to be banned from the bedroom as they can be a major cause of sleep disruption when snoozing on or near your bed.
11. Boost Melatonin Production
Melatonin is a hormone with many beneficial physiological activities in the body, including the regulation of our sleep-wake cycle, known as the circadian rhythm. It is largely produced in the evening in response to fading light to prepare us for sleep.
We’ve discussed how blue light exposure at night can affect melatonin production. However, other factors can also impede melatonin production such as jet lag, caffeine and lack of natural light during the day.
Luckily, you can make changes to increase melatonin production and improve sleep quality and quantity.
- Spend some time outdoors exposed to natural light each morning.
- Ask your doctor about a short-term melatonin supplement to help regulate your sleep-wake cycle and improve sleep quality (12).
- Reduce your consumption of coffee and soft drinks that contain caffeine (13).
- Increase your intake of melatonin-rich foods like milk, eggs, fish, mushrooms, cherries, tomatoes, nuts and seeds (14, 15).
12. Heal your gut
The gut — gastrointestinal (GI) tract — can have a massive impact on our sleep. Most people can relate to the disastrous effects certain food choices have on sleep.
GI symptoms like acid reflux can be really uncomfortable and are a common cause of disrupted sleep (14).
But the link between sleep and the gut goes further than this.
The gut microbiome — trillions of beneficial bacteria living in the GI tract — plays an integral role in many physiological processes. This includes contributing to the production of some important neurotransmitters and hormones like dopamine, serotonin, norepinephrine, melatonin and GABA (15). These neurochemicals influence stress and anxiety, so if the gut microbiome isn't optimal it can negatively impact our sleep.
However, the gut-sleep connection is a two-way street. A small study on healthy adults found that just two nights of poor disrupted sleep resulted in changes to the gut microbiome and shifted levels of important friendly bacteria (16). More research is needed in this area but these initial findings are not surprising, considering how important sleep is for overall health.
Focusing on healing your digestive system and boosting the health of your gut microbiome may be a key puzzle piece in the pursuit of quality deep sleep. Avoiding stress, antibiotics and refined sugary foods as much as possible is important for healing the gut, as well as increasing intake of fermented vegetables, a wide variety of plants and soothing bone broth. Consider supplementing with a probiotic if you struggle with digestive symptoms like bloating, cramps, IBS and acid reflux.
13. Rule out Medical Conditions
If you are still feeling tired and groggy when you wake up and aren’t getting sufficient sleep despite having made lifestyle changes, then you may need to consult a doctor. A sleep study can measure your breathing, heart rate, movements and brain waves while you sleep to assess your sleep cycles and see if you are reaching a state of deep sleep. This will help to identify and treat any hidden causes of poor sleep such as sleep apnea, restless leg syndrome or pain disorders.
14. Optimise your lighting Environment
Standard LED lighting in houses produce a very high amounts of blue light which causes strong wakefulness effects on humans, these lights at night are essentially sending signals to our brain that its the middle of the day and to stay alert and awake.
There is now research that has shown we have light receptors in our skin which directly have an affect on our circadian rhythm, so while Blue Blocking Glasses is protecting the harmful blue light from entering your eyes (where the receptors and light cues are the strongest), there is no protection being provided from artificial light hitting your skin which in turn is still causing circadian disruption.
“Campbell & Murphy (1998), in a bizarre experiment, shone bright lights onto the back of participants’ knees and were able to alter their circadian rhythms in line with the light exposure."
Using Red Nightlights and Light Bulbs low in blue light will completely remove the main source of stimulating blue light from within your home environment. Replacing your conventional bulbs with these will allow your body to know when its truly night time thus allowing you to easily and quickly fall into a deep and restful sleep.
15. Knowledge is Power: Track Your Sleep Stages
Take advantage of modern technology and track your sleep stages. One popular way to do this is through an Orua Ring.
How does the device even know you’re sleeping? Well, you’ll be physically at rest! Your lack of movement and lowered heart rate lets the device know that it’s your bedtime.
Your Orua Ring will track light sleep, deep sleep, and REM sleep. It will show you what percentage of your total sleep time was spent in each stage. Incredibly useful and personalized information is right at your fingertips.
This will help you find out what is and is not working when employing strategies to increase your deep sleep.
Resources
- Tassi et al. (2000). Sleep Inertia. Available at: https://www.ncbi.nlm.nih.gov/m/pubmed/12531174
- Not All Sleep Is Equal When It Comes To Cleaning The Brain. (2019). Available at: https://www.sciencedaily.com/releases/2019/02/190227173111.htm
- Deep Sleep Maintains The Learning Efficiency Of The Brain. (2017). Available at: https://www.sciencedaily.com/releases/2017/05/170523083345.htm
- World Sleep Day Talking Points. (2019). Available at: http://worldsleepday.org/usetoolkit/talking-points
- Dhand et al. (2006). Good Sleep, Bad Sleep! The Role of Daytime Naps in Healthy Adults. Available at: https://www.ncbi.nlm.nih.gov/pubmed/17053484
- Kubitz et al. (1996). The Effects of Acute and Chronic Exercise on Sleep. A Meta-Analytic Review. Available at: https://www.ncbi.nlm.nih.gov/pubmed/8726346
- Abbasi B et al. (2012). The Effect of Magnesium Supplementation on Primary Insomnia In Elderly: A Double-Blind Placebo-Controlled Clinical Trial. Available at: https://www.ncbi.nlm.nih.gov/pubmed/23853635
- Lanzi et al. (1999). Elevated Insulin Levels Contribute To The Reduced Growth Hormone (GH) Response To GH-Releasing Hormone In Obese Subjects. Available at: https://www.ncbi.nlm.nih.gov/pubmed/10484056
- Mindfulness Meditation Helps Fight Insomnia, Improves Sleep. (2015). Available at: https://www.health.harvard.edu/blog/mindfulness-meditation-helps-fight-insomnia-improves-sleep-201502187726
- Wienecke et al. (2016). Long-Term HRV Analysis Shows Stress Reduction by Magnesium Intake. Available at: https://www.ncbi.nlm.nih.gov/pubmed/27933574
- Burkhart et al. (2009). Amber Lenses to Block Blue Light and Improve Sleep: a Randomized Trial. Available at: https://www.ncbi.nlm.nih.gov/pubmed/20030543
- Lemoine et al. (2007). Prolonged-Release Melatonin Improves Sleep Quality and Morning Alertness in Insomnia Patients Aged 55 Years and Older and Has No Withdrawal Effects. Available at: https://www.ncbi.nlm.nih.gov/pubmed/18036082
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Shilo et al. (2002). The Effects of Coffee Consumption on Sleep and Melatonin Secretion. Available at: https://www.sciencedirect.com/science/article/pii/S1389945702000151
- Meng et al. (2017). Dietary Sources and Bioactivities of Melatonin. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5409706/
- Howatson et al. (2012). Effect of Tart Cherry Juice (Prunus cerasus) on Melatonin Levels and Enhanced Sleep Quality. Available at: https://www.ncbi.nlm.nih.gov/pubmed/22038497
- Shaker et al. (2003). Night Time Heartburn Is An Under-Appreciated Clinical Problem That Impacts Sleep and Daytime Function. Available at: https://www.ncbi.nlm.nih.gov/pubmed/12873567
- Strandwitz P. (2018). Neurotransmitter Modulation by the Gut Microbiota. Available at: https://www.ncbi.nlm.nih.gov/pubmed/29903615
- Sleep Loss Tied to Changes of the Gut Microbiota in Humans. (2016). Available at: https://www.sciencedaily.com/releases/2016/10/161025114118.htm
