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Sleep Inertia: What It Is and How to Overcome It

Medically Reviewed & Written By: Bobby Afshari (B.Pharm.MPS)
Last Updated: 16/09/2020


Have you ever felt groggy, disoriented, drowsy or tired upon waking up in the morning?

You may be experiencing the effects of sleep inertia or morning grogginess. It can affect anyone and usually lasts from 15-30 minutes to even 2-4 hours long.

According to clinical psychologist Dr. Michael Breus, “sleep inertia is the overwhelming feeling of sleepiness which makes it nearly impossible to get out of bed… (and) happens for a few reasons; theme here is that the person experiencing it usually wakes up in the middle of a sleep cycle”.

Sleep inertia is quite normal and can even happen to ‘good’ sleepers according to Dr. Breus. Upon waking up, a person may have trouble doing simple everyday tasks, may not feel as alert and may have their concentration impaired. In order to get rid of this heavy feeling, people usually rely on adrenaline from using loud alarm clocks or caffeine from their morning coffee. However, the good news is that sleep inertia is quite easy to overcome – it all comes down to making slight adjustments to both your morning and bedtime routine.

How do I stop sleep inertia?

Sleep inertia depends on:

  • the stage of sleep you are in upon awakening
  • how long you have been sleeping for
  • sleep deprivation
  • sleep efficiency

Sleep efficiency refers to the percentage of time a person sleeps, in relation to the total time spent in bed. A normal and healthy sleep efficiency is considered to be 85% or higher. Thus, your sleep efficiency is reduced when any of your sleep stages is interrupted by sudden awakening. As a result, a good night’s rest will allow your body to restore, hence reducing sleep inertia and increasing sleep efficiency. This means optimising both sleep quality and sleep quantity and can be achieved by sticking to a regular routine that will help regulate your body clock.

Although waking up naturally is the best way to avoid sleep inertia, it is not ideal as many people rely on an alarm for school or work. By being suddenly awakened, your melatonin levels are still high, thus causing drowsiness. To counter this, studies have shown that using natural light (ie. catching a glimpse of the sunrise through your window or even through an artificial dawn light) can help speed up the process of feeling fully alert and fresh upon awakening. It also suppresses melatonin levels, therefore decreasing the impacts of sleep inertia.

If you rely on an alarm, calculate backwards from the time you want to wake up in the morning to get an ideal sleep time. Multiply each cycle time , 90 minutes, by the number of sleep cycles per night, 5, to get 450 minutes (7.5 hours) of sleep and add an additional 15 minutes to doze off. For example, if you need to be awake by 7am, count back 7.5 hours plus 15 minutes – this means you should sleep around 11:15pm to get optimal sleep. Furthermore, rather than pressing the snooze button, try to set your alarm for when you definitely have to wake up. If you have trouble not pressing the snooze button, try placing it across your room so you are forced to wake up.

Research has also shown strategic napping may also help counteract sleep inertia, however the timing of the nap is critical; ideally 10-20 minutes in the afternoon is the sweet spot. However, a short nap is only effective if a person is not already sleep deprived.

Additionally, caffeine is something you’ve probably already thought about to eliminate the effects of sleep inertia. It helps people feel alert by increasing the amount of cortisol, a stress hormone, in your body and acts as a central nervous system stimulant. You may also try a stick of caffeinated gum as an alternative for coffee. Research has also shown that caffeinated gum helps reduce the effects of sleep inertia in shift workers after a nap.

Moreover you can practice good sleep hygiene to overcome sleep inertia:

  • Avoid using electronic devices at least 30 minutes before sleeping
  • Establish a regular bedtime routine: try reading a book or listen to some calming music to help you unwind
  • Avoid drinking alcohol before bedtime: contrary to how a glass of wine can make you feel sleepy, research shows that drinking alcohol too close to your sleeping time can disrupt your regular sleep time
  • Avoid drinking coffee or other caffeinated beverages before bedtime
  • Avoid eating a big meal close to bedtime: this can put pressure on your oesophageal sphincter, thus causing heartburn and disrupting your sleep. However, if you’re hungry, a light bedtime snack such as milk, kiwis and tart cherries have sleep promoting properties
  • Keep your bedroom dark and cool
  • Stick to a regular sleep routine

For more information, read our article on how to get a good night’s sleep here.

What causes sleep inertia?

Sleep inertia occurs when you suddenly wake up during slow-wave sleep or REM sleep. Immediately after waking from REM sleep, your melatonin levels are high, thus causing you to wake up feeling groggy. However, when you awaken during non-REM sleep, your heart rate, brain activity and blood pressure are slowed down, in turn helping you feel more alert and awake quicker. Sleep inertia is also caused by the buildup of adenosine, a neurotransmitter, within the brain during non-REM sleep. Other causes of sleep inertia include:

  • Slower brain reactivation: research shows that the prefrontal cortex (PFC), the region in our brain that is responsible for executive and cognitive function, takes longer to reactivate in the morning
  • Higher levels of delta waves & fewer levels of beta waves: these electrical waves are associated with deep sleep and wakefulness
  • Slow blood flow in the brain: research suggests that cerebral blood flow takes time to increase in velocity after getting up

Furthermore, sleep inertia may be worsened if a person is suffering from sleep apnea, a sleep disorder that results in partial or complete obstruction of the throat when a person in asleep. It is often associated with snoring, gasping, insomnia, headaches and extreme fatigue.

Is sleep inertia common?

Difficulty waking up is a common experience amongst the population – statistically, there is a 45% chance that an alarm clock will wake you up from REM sleep.

Within the first 3 minutes of waking up, your decision-making performance is reduced to 51%, and within 30 minutes may still be as low as 20%. However, your cognitive performance can be affected for up to 2 hours. The unpleasant and sometimes dangerous effects of sleep inertia also include:

  • Reduction in memory ability
  • Large amounts of caffeine affecting your heart
  • Morning stress
  • High adrenaline levels caused by a loud alarm clock
  • Impaired concentration
  • Impaired decision making
  • Lower response times on tasks
  • Drowsy driving: this accounts for 20% of road accidents (1.2 million accidents per year)

These effects can be highly dangerous for shift workers, pilots and bus drivers.

Why do I feel bad after a nap?

The familiar grogginess that occurs immediately after waking from a nap is caused by waking up mid sleep cycle – your brain is signalling that it wants more sleep so it can complete a full cycle. Thus, it is advised that napping is limited to no more than 20 minutes to prevent waking up during REM sleep. Post-nap disorientation and impairment may also last longer in those who over nap or those who are sleep deprived.

How is sleep inertia diagnosed?

If you are experiencing extreme distress and disrupt to your life, your doctor may diagnose you with severe sleep inertia. Recommendations are based on whether you are suffering from depressive disorders or other sleep disorders such as sleep apnea, whether you are a night shift worker, the level of your stress, and your overall lifestyle and heath. Your doctor may also conduct a sleep study to gather more insights into your sleep patterns.

However, if you are experiencing typical drowsiness and morning grogginess after waking up, try to establish a regular bedtime routine, avoid caffeine and alcohol in the evening, avoid eating large meals before sleeping and avoid over napping to overcome fogginess.

Ultimately, if sleep inertia is severely interfering with your ability to conduct daily activities, speak to your doctor and/or a sleep specialist to find the best treatments for you.

© 2020 CPAP Online Australia. All Rights Reserved.

Bobby Afshari (B.Pharm.MPS)

Bobby Afshari (B.Pharm.MPS)

Bobby Afshari studied a Bachelor of Pharmacy and is a member of the Pharmaceutical Society of Australia. Bobby is the sleep technician at CPAP Online Australia.

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