Sleep Inertia

Danielle Pacheco

Written by

Danielle Pacheco, Staff Writer

Dr. Anis Rehman

Medically Reviewed by

Dr. Anis Rehman, Endocrinologist

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Sleep is imperative to our health and wellness. Without adequate sleep, we wouldn’t have healthy physical and mental development.

Yet, some people may feel groggy and disoriented, even after receiving adequate sleep. This phenomenon is called sleep inertia. It is more common in people with alternative sleep schedules, like shift workers and military personnel. Sleep inertia can negatively impact reaction times related to important tasks like driving and decision-making.

Learning about sleep inertia’s causes, symptoms, and diagnostic process can be beneficial. Managing sleep inertia can also help ensure safety at work and home.

What Is Sleep Inertia?

Sleep inertia is the feeling of grogginess, disorientation, drowsiness, and cognitive impairment that immediately follows waking. Sleep inertia generally lasts for 15 to 60 minutes but may last for up to a few hours after waking. The biological reason for sleep inertia is unknown. However, researchers hypothesize that sleep inertia is a protective mechanism that helps maintain sleep during moments of unwanted wakings.

Regardless of its biological basis, sleep inertia can impact the safety and wellness of people who work long, frequently changing hours or shift work. Medical interns and residents who work rotating shifts or are on call regularly have a significant decrease in cognitive alertness and performance. At least 16% of U.S. employees engage in shift work. As a result, these workers might experience slowed reaction times and decreased cognitive alertness at work that increase the chance of work-related injuries.


The symptoms of sleep inertia are the most noticeable upon waking and slowly decrease over time. Sleep inertia symptoms can be present upon waking from a lengthy sleep period or naps over 30 minutes. The most common symptoms of sleep inertia are:

  • Grogginess
  • A desire to fall back asleep
  • Impaired cognitive ability
  • Impaired visual attention
  • Impaired spatial memory


The cause of sleep inertia is unknown, but there are three common theories explaining sleep inertia.

Increase in Delta Waves: Some research suggests that sleep inertia is caused by an increase in delta waves in the posterior part of the brain. Delta waves, or slow waves, are most commonly seen in the non-rapid eye movement stage of sleep. Delta waves are more likely to be increased after periods of sleep deprivation or loss. It may be that sleep inertia occurs when the brain has not yet reduced delta waves in preparation for waking up or is jarred awake during a non-rapid eye movement stage of sleep.

High Levels of Adenosine: Adenosine, a nucleic acid compound found in the brain, is a pivotal part in sleep and wakefulness. Upon waking, adenosine levels should be low. Research suggests that sleep inertia could be caused by high levels of adenosine upon waking due to prolonged sleep deprivation.

Reduced Blood Flow: The body’s blood flow to the brain follows a pattern corresponding to sleep cycles, with blood flow to the brain increasing or decreasing depending on the stage of sleep. Chronic fatigue syndrome (CFS) is linked to reduced cerebral blood flow. CFS symptoms are similar to sleep inertia, and it may be that a reduction in blood flow upon waking results in sleep inertia symptoms. However, more research needs to be done to support this concept.


Sleep inertia itself is not a sleep disorder, but people with certain sleep disorders are more likely to experience more severe or longer lasting sleep inertia. If you notice that you are feeling groggy or fatigued throughout the day, consider talking to your doctor about taking part in a sleep study, called a polysomnography. A sleep study can help your doctor determine if any underlying disorders are impacting your sleep and causing more severe sleep inertia.

Keeping a sleep journal may also provide your doctor insight into your sleeping patterns. Record times you sleep, as well as how you feel when you wake and any symptoms you experience. You may also want to check in with a partner for insight into your sleep and wake patterns. If you can pinpoint a trigger for your sleep inertia, like excessive caffeine use or inconsistent sleeping patterns, it may help to make lifestyle adjustments and record any change.


Although the exact cause of sleep inertia is unknown, there are ways you can adjust your lifestyle to facilitate better sleep and increase wakefulness.

  • Napping: Sleeping for a short period of time during a break at work may help you reduce sleep inertia. Naps are a common way people fit extra sleep into their day. Make sure that your naps are no longer than 30 minutes, as this may increase your risk of experiencing sleep inertia and difficulty falling asleep at night.
  • Caffeine Intake: Reaching for a cup of coffee or energy drink may help you feel more awake in the morning. A desire for increased alertness might be why, worldwide, over 1.6 billion cups of coffee are consumed each day. Caffeine works by blocking adenosine receptors in the brain, which increases wakefulness and alertness. However, too much caffeine may negatively impact your sleep.
  • Light Restriction: Keeping your sleep and wake cycles in alignment with the natural rise and fall of the sun may help reduce sleep inertia. Studies show that artificial light can impact the body’s natural circadian rhythm and disrupt sleep when viewed later in the day. Adjusting the light in your bedroom through room darkening curtains may help you get more restful sleep.
  • Temperature Adjustments:  Sleeping in a room that is too hot prevents your body from cooling before sleep, resulting in fatigue. Try adding a quiet fan to your room or adjust the blankets on your bed. During summer, consider investing in a small air conditioner unit or lightweight pajamas.
  • Gentle Waking: Many alarm clocks can be jarring and loud, which could increase feelings of confusion or grogginess upon waking. Try opting for a smart alarm clock app that registers when you are in a light state of sleep. Or, try a sunrise alarm that wakes you with gradually increasing light and gentle sounds.



When to Talk to Your Doctor

For most people, the symptoms of sleep inertia generally pass within an hour. If your sleep inertia lasts longer than that, or if you experience excessive daytime sleepiness throughout the day, talk to your doctor. Also, if you experience difficulty talking, trouble understanding what others are saying, or a loss of coordination along with confusion, immediately call 911 as these may be signs of a stroke.

Additional Sleep Tips

Finding the right way to sleep is easier said than done, especially if you sleep with a partner. Engaging in a good sleep hygiene routine can help you obtain better sleep. Additionally, you can try the following tips for better sleep:

  • Pick the Right Bedding: Find the best mattress and bedding to feel comfortable at night. Research has found that people who upgraded their mattress and bedding experienced less pain and had an increase in sleep quality.
  • Diffuse Essential Oils: There is evidence to suggest that scents like lavender have a calming effect and promote relaxation.
  • Keep a Consistent Schedule: Set a fixed sleep and wake time, even during the weekend and vacations.
  • Avoid Electronics Before Bed: Try increasing the time apart from devices gradually, starting with five minutes before sleep.
  • Exercise Daily: Exercise has been shown to have a positive impact on sleep quality. For best results, try to avoid exercising right before bed.
  • Avoid Alcohol and Smoking: Drinking alcohol in excess can increase your risk for heartburn, which can impact your ability to comfortably fall asleep. Smoking has been associated with sleeping problems such as trouble falling asleep and low sleep satisfaction.
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About Our Editorial Team

Danielle Pacheco

Staff Writer

Danielle writes in-depth articles about sleep solutions and holds a psychology degree from the University of British Columbia.

Dr. Anis Rehman



Dr. Rehman, M.D., is a board-certified physician in Internal Medicine as well as Endocrinology, Diabetes, and Metabolism.


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