When waking up in the morning is the hardest thing to do, thank sleep inertia. Sleep inertia is the period of arousal where you feel disoriented, confused, or just incredibly sleepy. You might have trouble doing routine tasks like walking to the bathroom or replying to a text.
Now these symptoms may sound worrisome but trouble waking up is a very common and natural experience, especially for teens, young adults, and shift workers. People who tend to be night owls may also be more likely to experience extended sleep inertia during workdays due to their natural sleep schedule.
Though sleep inertia can last up to two hours, the grogginess normally subsides within about 30 minutes for people without sleep deprivation, according to the Centers for Disease Control and Prevention (CDC). Longer periods of sleep inertia can be challenging for people who perform important safety-related tasks at work or operate vehicles and machinery.
If you feel like you’re having a hard time waking up in the morning, keep reading to find out the potential cause and steps you can take to the transition from when you just can't wake up.
What causes sleep inertia?
Researchers have noted that poor sleep can make sleep inertia worse. While the following causes are known to increase sleep inertia, remember that they themselves may have other underlying conditions and triggers. Mental health disorders, delayed sleep phase, and sleep disruptors can all prevent you from getting a full night of sleep.
1. Waking up during deep sleep or in the middle of the night
The main underlying cause of sleep inertia seems to be as simple as waking up in the middle of stage 3 sleep (deep sleep), explains Dr. Aneesa M. Das, a sleep medicine specialist at Ohio State University. Deep sleep is the "most difficult to wake from stage" of your sleep cycle, and it’s critical for physical and mental restoration. If you nap for more than 30 minutes and are jolted awake, you may be waking up in the middle of deep sleep.
However more recent studies also note that the quality of your sleep and your wakefulness before can also influence the relationship between deep sleep and sleep inertia. For example, if you are waking up frequently at night, you may not be getting enough deep sleep either and could feel less restored in the morning.
2. Sleep loss or sleep deprivation
If you use an alarm to wake up, then, by definition, you’re not sleeping until you’re fully rested, says Dr. Michael Awad, chief of sleep surgery at Northwestern Medicine. This could be a result of late bedtimes or chronic sleep deprivation. Research shows that after a night or multiple nights of sleep deprivation and sleep restriction, performance is worse after waking.
Sleep deprivation can also reduce the amount of time between falling asleep and moving into stage 3 sleep. “As soon as you fall asleep, your body will try to go straight into the sleep stage of which it’s deprived,” Awad says. However if you don't get enough hours of sleep, you may be missing out on other restorative sleep stages.
3. Disrupted circadian rhythms and natural chronotypes
Circadian disorders can increase your propensity for sleep inertia, Awad says. One study investigated the severity of sleep inertia and found that where your circadian phase is, upon waking, can impact speed and accuracy when completing tasks.
Sleep inertia is strongest when you are at “circadian low.” While this is usually at night, an out-of-sync circadian rhythm could be “low” in the morning. Circadian rhythm sleep disorder can also be an underlying cause of overall sleep disruption and loss.
4. Idiopathic hypersomnia (IH)
Sleeping for more than 12 hours in a 24-hour period, without a known medical cause, is known as idiopathic hypersomnia. With IH, sleep inertia is more commonly known as sleep drunkenness because it lasts up to four hours and has more severe symptoms like slurred speech, amnesia, and confusion.
7 ways to combat extended sleep inertia
“[Sleep inertia] can become a problem when it compromises your ability to safely do things,” says Awad. An example is rushing out of bed because you’re trying to get more snooze time and, as a result, react slower in thinking, responding, reasoning, and remembering.
Sometimes the stakes are high: Driving with sleep inertia could cause accidents. But even when the stakes aren’t that high, sleep inertia can be an awful way to start the day.
While there are currently no direct solutions for sleep inertia, researchers have investigated several habits and practices that may minimize its impact.
Here are ways to transition towards self-awakening, from immediate to long-term solutions:
1. Plan extra time for your sleep inertia
Wanting to go back to sleep can be frustrating but remember 30 minutes of grogginess is normal. Rather than hitting snooze and getting out of bed at the last minute to get “more” sleep, plan for that transition with simple morning activities that don’t require making important decisions.
Try morning yoga to get the blood flowing. You can also plan the night before by writing a morning to-do list so you don’t have to rely on early morning decision-making.
2. Wake up with caffeine
“To a certain degree, [caffeine] can help you get over sleep inertia relatively quickly,” Awad says. He stresses that drinking coffee, tea, or any other caffeinated beverage should only be in the morning.
Drinking caffeine in the afternoon or evening can increase the risk of insomnia, sleep deprivation, and more sleep inertia. This is because caffeine is an adenosine suppressor, which means caffeine suppresses the substance in your body that prevents wakefulness so that you can feel alert.
3. Take a cold shower
As shocking as you can imagine cold showers to be, that shock does have some emerging science behind it. Early research suggests that extreme cold can speed up recovery from sleep inertia, however researchers note this relationship needs more investigation.
Cold showers have other benefits too: Studies on the effects of cold showers also noted that people who took cold showers reported 29% fewer sick days. But if a cold shower sounds like too much, simply rinsing your hands and feet with cold water may also do the trick.
4. Use a sleep-stage-based alarm
If you need to use an alarm for waking, it can be helpful to use a sleep-tracking app, Awad says. Sleep trackers use your movement patterns and heart rate to determine what sleep stage you’re in, and some have alarms that use this data to wake you during a light stage of sleep — within a window of time you designate — so you are waking at a time most in sync with your body’s circadian rhythm.
Researchers have not landed on how sound affects sleep inertia (the theory is that pop music may be more effective) but Awad also notes that alarms are not a replacement for sleep hygiene.
5. Keep naps under 30 minutes
The shorter and more strategic your naps, the less opportunity your body has to make its way into deep sleep.
If you find yourself frequently needing hour-plus naps or if you experience sleep inertia even after short naps, it’s worth taking a look at your overall sleep quality, Awad says. Address any underlying issues that could be contributing to sleep deprivation.
6. Turn up the lights
If a shifty circadian rhythm has you saying you can’t wake up, try light-exposure therapy. The CDC notes that bright light in the morning can help you shift towards an earlier bedtime, potentially countering sleep loss. “It acts on receptors in the eyes to decrease production of melatonin and encourage wakefulness,” says Das.
7. Sleep and wake up at the same time
“When a person is well trained for sleep, they go to bed and wake up around the same time every day without an alarm clock,” Awad says. Waking up at the same time can help with circadian rhythm disruption. “The body will naturally wake up when you’ve achieved sufficient sleep.”
To train, keep a consistent sleep schedule for a full night of sleep. This allows for you to go through your sleep cycles, lowering your risk of waking up during deep sleep or before you’ve gone through the cycles.
You may need to use an alarm at first to help wake you up at the same time, but if you’re getting enough hours of sleep to achieve quality sleep, you should eventually wake up on your own.
But why does sleep inertia exist?
At first glance, a groggy transition period between sleep and wake doesn’t seem like the most evolutionary adaptation. Wouldn’t it be better and safer for us to be able to flip the switch immediately? The anxious, grind-culture part of us may believe so, but sleep researchers theorize that sleep inertia may also have a protective benefit.
One theory for why sleep inertia exists is that it helps maintain sleep, for when you don’t want to wake up like awakenings in the middle of the night. If you do awaken, your brain needs time to reorganize its networks. Researchers have observed that blood flow is slower during this time, up to 30 minutes after waking, which explains our slower cognitive functions.
Awad also explains that adenosine, a substance which causes sleep and decreases arousal, may play a role. Adenosine is a natural byproduct of the body’s breakdown of carbohydrates, protein, and fat into energy throughout the day. It’s the buildup of adenosine that triggers sleepiness.
“Adenosine levels are very high late at night to help initiate sleep, and it’s possible that upon waking, some adenosine molecules are still bound to receptors in the brain,” he says. If you did not get enough sleep, your adenosine levels may not be cleared yet.
However, these theories are not completely understood, and what may be causing your sleep inertia (like adenosine buildup) may be different from someone else. Sleep experts still have more to learn about sleep inertia and its role in sleep health.
If you’re experiencing severe sleep inertia, like sleep drunkenness, make an appointment with your health care provider to see if there is an underlying cause. But if it isn't a defining sleep experience, it’s probably not something to worry about.
Instead, focus on practicing sleep hygiene habits and syncing your circadian rhythm for natural wake ups. In time you may start to experience shorter periods of sleep inertia.