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What is deep sleep

Sleep can be broken down into different ‘stages’ of sleep. Most commonly, sleep is divided into rapid eye movement sleep (REM) and non-REM (NREM) sleep. NREM sleep accounts for the majority of sleep (75-80% of total sleep duration), while REM sleep makes up the rest. Within NREM sleep, there are four stages; the first stage is light sleep and is mostly the transitory onset of sleep; the second stage is also considered light sleep, but makes up a longer duration than stage 1.

The third and fourth stages are considered ‘deep sleep’ and are characterized by slow brain waves. Deep sleep makes up roughly 13-23% of nightly sleep. It is during these stages that sleep is restorative and leads to many adaptive physiological outcomes that help the body adapt and repair. As such, deep sleep has been shown to be more important than total sleep time in affecting physiological outcomes.

How it is measured

Deep sleep is often identified by slow waveforms on an electroencephalogram (EEG), which measures brain wave activity. As an alternative, deep sleep has been shown to have decreased movement and altered vital signs, particularly: lower heart rate, higher heart rate variability, lower blood pressure, lower temperature, and decreased sympathetic activity, among others.

By measuring these changes using wearable technologies (accelerometers and photoplethysmography [PPG]), a close approximation of sleep stage can be made. Using this technology allows for passive measurement with much less equipment than a traditional EEG or polysomnogram.

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Correlation with health conditions

Much like with total sleep time, the restorative benefits of deep sleep have robust physiological effects across many organ systems. However, deep sleep appears to be a better indicator of the quality of sleep, compared to the total duration of sleep.

Deep sleep has been shown to affect growth hormone production, glucose metabolism, synaptic processes (e.g. learning/memory formation), and immune function changes. Sleep restriction, affecting the duration of deep sleep, has been linked to many negative health outcomes, including cardiovascular disease, diabetes, neurodegenerative diseases, poor cognitive function, and many more conditions. As such, it is important to get adequate amounts of sleep that is of good quality, permitting deep sleep.

Normal or acceptable range

Currently, there are not widely accepted values specific to deep sleep. There appears to be an age-related decline in the duration of deep sleep, with minimal change in other sleep stages, in absolute terms. Of each sleep session, most individuals have 13-23% of their duration in deep sleep. The recommended amount of deep sleep has not fully been evaluated, but many experts believe that it is better to have more than less, although high amounts of deep sleep may indicate short term deficiencies.

Interpreting trends

While it is relatively easy to approximate total sleep time by tracking sleep and wake times, deep sleep is much harder to quantify. Use of EEG devices provide a strong understanding of sleep stages and progressions but are less obtainable for an individual on a regular basis. However, using accelerometers and PPG wearables, such as Biostrap, light and deep sleep can be approximated on a nightly basis, and easily tracked over time.

As with total sleep duration, tracking deep sleep can provide insight into its contribution to changes in physiological variables, cognitive and/or athletic performance, mood, fatigue, and other health-related outcomes. As a variable that is more challenging to quantify, monitoring deep sleep over time can also provide insight into lifestyle changes and how they affect deep sleep. For example, tracking how a medication affects deep sleep may provide insight into its efficacy or side effects.

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When it comes to getting enough sleep, we have a habit of trying to cut corners. Seven or eight hours of sleep may sound ideal, but rarely do we seem to have the time.

According to the National Sleep Foundation, older adults should sleep between 7-9 hours each night. This recommendation only increases amongst teenagers, preschoolers, and toddlers. Yet despite this advice, 45% of Americans say that poor or insufficient sleep has affected their daily lives at least once in the past week.

Getting a good night’s sleep isn’t easy, but it’s essential. Let’s pull down the sheets to learn more about sleep, why 6 hours of sleep simply isn’t enough for most people, and what we can do to ensure we’re getting the hours of shuteye we need.

The Basics of Sleep

There are four primary stages of sleep to be aware of, and we collectively refer to these stages as the sleep cycle.

The first stage is the lightest stage of sleep when you’re just dozing off. During this stage of drowsy sleep is when you may experience slight twitching such as Hypnic jerks, and you can also easily be woken. Your muscles will relax and your brain will begin to slow down as your body prepares for a more restful, deep sleep.

The second stage of sleep is when body temperature will begin to drop and heart rate and breathing rate both slightly decrease. You can’t be woken as easily during this stage of sleep, and your brain will continue to slow down as bursts of brain activity called sleep spindles occur. Research suggests sleep spindles protect the brain from awakening during sleep.

The third stage of sleep is known as slow-wave sleep. This is the most restorative stage of sleep and is marked by delta brain waves. Some of the most essential bodily processes occur during this stage including hormonal balancing, human growth hormone release, brain detoxification and memory consolidation.

The fourth and final stage of sleep is known as rapid eye movement, or REM, sleep, and this is where dreaming takes place. While your muscles will be “paralyzed”, brain waves will become more active, behaving nearly as if you were awake. Getting an adequate amount of REM sleep is very important for cognitive functions as well as memory. 

Generally speaking, your body will spend more time in deep sleep during the first half of the night and more in REM during the second half.

Ensuring you reach each of these four stages of the sleep cycle is extremely important. One sleep cycle, which will include all four stages of sleep, will often last approximately 100-120 minutes, and you’ll transition through four or five full cycles per night.

For Most Of Us, 6 Hours of Sleep Isn’t Enough

We hate to burst your bubble, but six hours of sleep just isn’t enough for the average individual. While some people do well on only six hours of sleep, most of us would benefit from an extra hour or two of additional rest. Below we’ve included the nine primary sleep groups identified by the Centers for Disease Control and Prevention, along with their corresponding sleep recommendations.

Newborns
​Newborns should receive between 14 and 17 hours of sleep, though 11 to 13 hours is acceptable as well. Ultimately, newborns shouldn’t sleep less than 11 hours per day.

Infants
Infants should sleep between 12 and 16 hours, including naps.

Toddlers
Toddlers should sleep between 11 and 14 hours each day, including naps. Toddlers shouldn’t sleep less than 9 hours per day.

Preschoolers
Preschoolers should sleep between 10 and 13 hours per day, including naps.

Children (6-12 years of age)
Children should get 9 to 12 hours of sleep.

Teens (13-18 years of age)
Teens should get 8 to 10 hours of sleep per day.

Adults (18-60 years of age)
Young adults should get 7 to 9 hours of sleep per day.

Older Adults (61-64 years of age)
Older should get 7 to 9 hours of sleep per day.

Seniors (65 years of age and older)
Seniors should get at least 7 to 8 hours of sleep each night.

Is 6 Hours of Sleep Enough for You?

While 6 hours of sleep isn’t enough for most of us, there are signs you can watch for to determine if 6 hours of sleep is enough for you. For instance, yawning, fatigue, brain fog, and irritability are telltale signs that you’re simply not getting enough sleep.

Other symptoms of tiredness or sleep loss include a lack of motivation, clumsiness, and increased appetite. If you’re sleeping for six hours or less per night while experiencing these symptoms, you’ll need to increase the amount of sleep you’re getting to reflect nightly recommendations for your age, or you’ll need to find ways to improve upon your quality of sleep.

Did you know that Biostrap offers an advanced sleep tracking and analysis feature? In addition to the basic sleep offerings, the Biostrap Sleep Lab provides more frequent biometric recordings (up to every two minutes), plus after a 15-day baseline, you can get personalized sleep time and wake-up time recommendations to help optimize your circadian rhythm and achieve improved sleep quality and recovery. 

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Why Aren’t You Getting Enough Sleep?

Poor sleep or a lack of sleep can often be attributed to a number of factors. From taking sleep for granted to consuming caffeine before bed, sleep problems are widespread. Below you’ll find the common reasons people don’t get enough sleep.

Stimulants

Stimulants such as caffeine, alcohol, and even sleeping pills can interfere with your ability to fall asleep and stay asleep. While substances like alcohol may evoke the feeling of sleepiness, in reality, your sleep will be very restless. Sleeping medications, on the other hand, may be okay to use occasionally, but these become less impactful over time, and you may become dependent on them to fall asleep.

Shift Work

Those who work changing shifts have a more difficult time establishing a consistent sleep-wake pattern. While some adjust to these changes better than others, shift work can influence your circadian rhythm and drastically reduce the amount of sleep you should be getting each night.

Eating & Drinking Late

Eating late may impact the quality of your sleep. Going to bed on a full stomach will not only keep your body busy digesting what you just ate, instead of focusing on sleeping, but as elevated blood sugar levels trigger an insulin response, it can also cause a spike in cortisol which will keep you from transitioning into the sleep stages mentioned above.

Not to mention, certain unhealthy food choices may even cause heartburn, chest discomfort or bloating that may keep you up at night.

As a result, it’s best to avoid any late night snacks before bedtime. If you’re hungry, eat something small, such as a teaspoon of nut butter, and drink a glass of water or a cup of tea. 

Stress

Stress may keep us up at night and disrupt our sleep schedule. Elevated stress levels may keep your fight-or-flight, or sympathetic nervous system, activated, blocking your chance to tap into the parasympathetic, rest-and-digest, nervous system and get a restful sleep. Give yourself a chance to relax and unwind before bed — meditate, journal or do some breathwork — to help your body wind down. If stress is still stopping you from getting quality sleep, speak with your doctor to find techniques for coping with stress.

Sleep Disorders

​Sleep disorders are one of the most common reasons we suffer from sleep deprivation. Sleep apnea, night terrors, insomnia, and more can influence our sleep habits for days or even years at a time. If you suffer from a chronic sleep disorder that stops you from getting a good night’s sleep, consider talking to your doctor to determine what you can do to get back to bed.

Healthy Habits to Develop

Our body’s circadian rhythm is always telling us when it’s time to sleep and when it’s time to wake up. When this internal rhythm is disrupted, however, we’re left with a myriad of negative consequences leading to poor sleep. With this in mind, here are some tips on how to improve your sleep patterns so that falling asleep becomes a breeze.

Follow a Sleep Schedule

It may seem like a no-brainer, but your body prefers a sleep schedule that allows you to fall asleep and wake at the same time each day. This can also reduce your risk of heart disease, which sleep deprivation can increase your risk of developing.

Watch What You Eat

Avoid heavy meals close to bedtime and keep snacking to the minimum. Drinking water or tea before bed is healthy, but too much fluid can result in frequent bathroom trips that negatively impact your sleep duration.

Avoid Bedtime Distractions

Bedtime distractions such as digital screens, bright lights, and loud music can stop you from getting a good night’s sleep. Consider turning off your phone, dimming the lights, and reading a book before bed to allow your body and mind to wind down. A healthy bedtime routine that’s free of distractions will put your head in the right place before it hits the pillow.

Sleep Medicine

Though sleep medicine isn’t recommended for everyone, certain individuals may benefit from sleep medications that aid in falling asleep. If you find yourself suffering from a lack of sleep on a consistent basis, talk to your doctor to determine if sleep medicine is the right avenue for you.

So, Is Six Hours of Sleep Enough?

At the end of the day, six hours of sleep isn’t really enough for the average person. While we all know someone that functions well on less sleep, the side effects that come with a lack of sleep such as weight gain and compromised cognitive performance are reason enough to ensure you’re getting your recommended amount of sleep. While getting the sleep your body craves can be difficult, every hour of sleep you get makes an impact on your overall health.

Consider tracking your sleep with the most advanced digital health solution that’s available right now. Gain valuable insights into your sleep quality and start introducing a data-driven approach to understanding how your lifestyle choices are making an impact on your sleep and recovery.

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Have you ever found yourself falling asleep only to suddenly wake up because your body twitches? Maybe it feels like a jerking contraction you can’t control, as if your body convulses all at once. If you’ve ever encountered this strange sensation, then you’ve experienced what’s referred to as a hypnic jerk.

Also known as hypnagogic jerks or sleep twitches, a hypnic jerk is an involuntary twitch that occurs as your body transitions from being awake to falling asleep. And though they may seem foreign in nature, research suggests that 60-70% of people experience sporadic hypnic jerks from time to time.

What Is a Hypnic Jerk?

Let’s start with a few of the basics. By definition, hypnic jerks (a.k.a. sleep starts, hypnagogic jerks, or myoclonic jerks) are nothing more than your body twitching as it transitions into the first stages of sleep. Named for the transitional period between being fully awake and falling asleep, the hypnic jerk is a harmless condition experienced by many.

Believe it or not, a hypnic jerk is very similar in nature to a common hiccup. Both a hiccup and a hypnic jerk are considered an involuntary muscle twitch known as a myoclonus.

Hypnic Jerk Symptoms

Because a hypnic jerk isn’t a disorder, it’s important to note that any symptoms you may experience aren’t cause for concern. Instead these symptoms are simply things you might experience while transitioning into a state of sleep. They include:

  • Falling sensations
  • Sweating
  • Rapid heartbeat
  • Jerking or rapid limb movements
  • ​Fast breathing
  • Dreams or hallucinations that lead to a startle

What Causes a Hypnic Jerk?

Unfortunately researchers haven’t been able to uncover exactly why the hypnic jerk occurs because both healthy and unhealthy people experience it. Theories, however, do exist that offer plausible causes.

Sleep Deprivation

As is the case with so many sleep disorders, some believe the hypnic jerk occurs due to poor sleep habits or sleep disturbances. For this reason, it’s pertinent that you develop a healthy sleep routine by sticking to a consistent sleep-wake schedule. Consider utilizing a sleep tracker to monitor your sleep patterns and gain a better understanding of your sleep.

Exercise

Exercising each day is important no matter your current state of health. However, some believe exercising before bed may cause your brain and muscles to remain active as you try to fall asleep. This may lead to side effects that include sweating, jerking, or frequent awakenings throughout the night.

Stress

Anxious thoughts and emotional stress can keep you tossing and turning at night when all you want to do is sleep. Because sleep is a healing period for both the mind and body, it’s quite possible that stress is causing your muscles to alert your body, even as it drifts off to sleep. Such alerts can occur in the form of twitches and jerks.

Stimulants

Nothing stops your body from falling asleep quite like stimulants do. Be it caffeine, nicotine, or any other stimulant, these substances can negatively impact your body’s ability to fall asleep and to reach deeper stages of sleep, like rapid eye movement (REM) sleep or slow-wave deep sleep.

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Evolution

Some research suggests the hypnic jerk is simply an evolutionary trait passed on to us by our ancestors from thousands of years ago. This may be the case when you consider that primitive humans slept in trees and, therefore, needed to ensure they wouldn’t wake up only after falling to the ground. The hypnic jerk may have once served us as an alert to readjust our sleeping positions while dozing in branches high above.

Who Experiences Hypnic Jerks?

While hypnic jerks can affect everyone, the American Academy of Sleep Medicine notes that adults are far more likely than children to experience hypnic jerks. The reason for this pertains to specific factors that affect adults rather than children, such as stimulant intake, emotional stress, and intense bouts of exercise. Hypnic jerks may still occur in children, but they are far less common.

Hypnic Jerk Treatments

Because the hypnic jerk isn’t considered uncommon or unhealthy, prevention is more adequate to stop it from happening in the first place. Follow the steps below that aim to help you transition into sleep and sleep soundly throughout the night.

Practice Good Sleep Hygiene: Sleep hygiene is nothing more than a fancy term for healthy sleeping habits. In order to sleep better, you first need to provide your body with a few basic essentials. These include exercising regularly, limiting exposure to digital screens a couple of hours before bed, avoiding bedtime snacks, and steering clear of stimulants that can keep you awake. Temperature also plays an important role, so make sure to check our our article on The Best Temperature for Sleep

Avoid Stimulants: Stimulants act as powerful shots of energy that flood your brain and body and keep you going. As enticing as that may sound at two o’clock in the afternoon when you grow drowsy, it does no good for your brain later in the night. Avoid caffeine, nicotine, alcohol, or other stimulants beyond midday, as these are likely to keep your physiology from being able to wind down when it’s time to sleep. And remember that while alcohol or wine may make you drowsy before bed, chances are they’ll disrupt your sleep later in the night. If you track your sleep with a Biostrap’s wrist-worn device, you may notice changes in your sleep patterns as well as biometrics, such as heart and heart rate variability.

Exercise Timing: While some of us enjoy being productive at night rather than during the day, do your best to complete any intense workouts by mid-afternoon. And if this isn’t possible, focus on low-intensity exercise in the evening, such as a walk after dinner, that won’t keep your heart racing into the night.

Breathing Exercises: Breathing exercises are an effective way of slowing down your heart rate, activating your parasympathetic (rest and digest) nervous system, and getting a restful night’s sleep. Consider utilizing a breathing technique known as “box breathing” that’s taught to Navy Seals. This technique aims to slow your heart rate and reduce stress by performing a specific breathing cycle for a short period of time: inhale for a count of 4, hold for a count of 4, exhale for a count of 4 and hold for a count of 4. Repeat this four times.

As unusual as the hypnic jerk may seem, following these simple tips will reduce the likelihood that hypnic jerks will disrupt your slumber. If your experience with hypnic jerks doesn’t improve after adopting these preventative options, consider talking with a licensed health clinician to discuss your options.

Living With Hypnic Jerks

While the hypnic jerk may come across as an unhealthy or unnatural occurrence, in truth, it’s a completely normal experience that many of us know well.

If your experience with hypnic jerks has you concerned or is keeping you awake, don’t be afraid to speak with your doctor or a licensed healthcare provider to discuss your treatment options.

If you find yourself experiencing hypnic jerks regularly, consider making an appointment with your doctor as this may be a symptom of poor sleep patterns or lingering stressors.

At the end of the day, remember that hypnagogic jerks aren’t uncommon, nor are they a disorder. Take some time to relax before bed, treat your body well, and you will reduce the likelihood that you’ll wake due to an unforeseen twitch.