What Is Sleep Inertia?
Sleep inertia, sometimes referred to as electroencephalographic sleep inertia, is viewed as a distinct state of consciousness different from sleep and wakefulness. During sleep inertia, a person may be extremely sleepy and experience physical and cognitive performance impairment.
People often refer to sleep inertia as "grogginess." In some cases, sleep inertia is also called "sleep drunkenness," though experts view it as distinct from and more severe than sleep inertia. Sleep drunkenness is often associated with sleep disorders, while sleep inertia can happen to anyone.
If you've been experiencing sleep inertia, you may be wondering what it is, what causes it, and if it's a symptom of a sleep disorder. Understanding the symptoms and causes of morning sleep inertia and sleep inertia at other times of the day may be helpful when seeking support.
Sleep inertia symptoms
Sleep inertia symptoms often include but are not limited to the following:
- Extreme sleepiness
- Disorientation
- Confusion
- Difficulty thinking clearly
- Difficulty focusing
- Poor memory
- Reduced decision-making ability
- Reduced performance
When a person experiences sleep inertia, their performance may be reduced in various areas. For example, studies have found that people with sleep inertia take longer to complete addition and subtraction tasks and make more mistakes. A person's reaction times are slower during sleep inertia, and performance regarding movement and tracking visual stimuli is impaired. When people make decisions during sleep inertia, they are less likely to think through the relevant details and more likely to make choices using shortcuts or biases.
When do symptoms of sleep inertia occur?
Sleep inertia can occur at any time of day after a person has just woken up. Sleep inertia can happen in the morning, in the afternoon after a short nap, or when waking up to go to the bathroom at night. Sleep inertia isn't solely a result of being sleep-deprived. This symptom can occur even after a complete night of quality sleep. However, sleep inertia may be more likely in the following scenarios:
- When waking during a person's biological night (the time they usually are asleep)
- After a night of partial sleep deprivation
- After a night of extra recovery sleep following a previous night of sleep deprivation
- When a person has ongoing sleep debt
- When a person is a "night owl"
- After longer (but not shorter) naps
- When waking from the deep sleep stage
How long does sleep inertia last?
Some individuals’ performance may not return to normal until they've been awake for two or three hours. The subjective sensation of sleep inertia may only last 30 to 60 minutes, but the performance effects of sleep inertia could last longer than most people are aware of. Some experts suggest that subjective experiences of sleep inertia don't adequately describe the phenomenon, and performance tests may better measure the symptom.
What causes sleep inertia?
Experts aren't entirely sure why people experience sleep inertia, but some think it could be an adaptive tool that helps people fall back asleep when they wake up during a period of sleep. Others have hypothesized that sleep inertia could help people gradually shift from rapid eye movement (REM) sleep to wakefulness so dreams don't intrude on waking life. More research is needed to understand the cause of sleep inertia fully.
Although experts don't know why sleep inertia happens, studies have provided insight into what is happening physiologically during sleep inertia. For up to 30 minutes after waking, cerebral blood flow velocities are lower than their pre-sleep levels. This reduction in cerebral blood flow to certain parts of the awakening brain may explain a decrease in performance. Imaging has shown that specific parts of the brain, such as the prefrontal cortex, which is responsible for executive function, take longer than others to return to normal after waking.
Risks of sleep inertia
The most significant risks of sleep inertia are experienced by those with careers requiring them to engage in work or make serious decisions immediately after waking up. For example, emergency responders, military members, pilots, and night shift workers may have sleep inertia that impacts them more severely than those who usually wake up and begin work at consistent, predictable times every day. Also, they may be more likely to work, drive, operate machinery, or make complex decisions shortly after having woken up while still affected by sleep inertia, which may be dangerous.
Experts believe that the adverse effects of sleep inertia seen in studies may carry over to have real-world effects for people who must work or make decisions shortly after waking up. Some research on night shift workers, such as nurses and emergency pilots, reflects this. For example, in a study of over 400 Air Force piloting accidents, researchers found that accidents caused by pilot error most commonly occurred in the first hour after waking up, which suggests sleep inertia may play a role.
When to seek medical help
If sleep inertia is extreme, involving severe confusion, discoordination, and slowness lasting up to four hours, it may be sleep drunkenness. Sleep drunkenness is a severe form of sleep inertia often associated with specific sleep disorders, like idiopathic hypersomnia and certain circadian rhythm disorders. If you believe you have sleep drunkenness, consider seeing a doctor for testing.
Sleep inertia lasting 30 to 60 minutes after waking is normal and doesn't necessarily indicate that a person has an underlying sleep disorder or other illness. Sleep homeostatic drive builds up one’s ability to wake up and function regularly when an individual first wakes. However, sleep inertia can be difficult to distinguish from other symptoms, like fatigue and daytime tiredness. People who are sleep-deprived may also struggle to wake up and be alert in the mornings due to a persistent desire for more sleep.
Various sleep disorders, including obstructive sleep apnea, narcolepsy, and circadian rhythm disorders, can cause excessive tiredness in the morning or at other times of the day. Physical and mental illnesses, including depression, can cause fatigue. If you struggle to stay awake during the day or are more fatigued than usual for an ongoing period, see your doctor. Your doctor can ask you relevant questions and help you determine if an underlying disorder is present.
Therapy for insomnia, sleep inertia, and other sleep disorders
While sleep inertia can be a normal phenomenon, some people wake up tired because they couldn't get enough sleep the night before, despite trying. This condition is insomnia. Insomnia can involve difficulty falling asleep, difficulty staying asleep, and waking earlier than intended without being able to fall back asleep. The first-line treatment for insomnia is often cognitive-behavioral therapy (CBT).
Some people may prefer remote therapy for insomnia. Remote therapy allows you to meet with a therapist virtually, from your home, or wherever you prefer, with a Wi-Fi connection. If you're struggling with energy and alertness, remote therapy could be beneficial since it allows you to avoid traveling to a different location to speak with someone face-to-face. Through an online platform like BetterHelp, you can receive support via phone, video, or live chat and access unique resources like support groups and worksheets.
A randomized, controlled trial compared face-to-face cognitive behavioral therapy for insomnia (CBT-I) with CBT-I delivered via an online platform. Researchers found that CBT-I delivered remotely was as effective as CBT-I delivered in person and helped people improve their sleep and daily functional ability. The study authors also noted that remote therapy could be more efficient than in-person sessions in some cases.
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