Sleep Inertia: Why You Feel Groggy and How to Manage It

Feeling drowsy when you first wake up is normal. It’s called sleep inertia. We’ll explain why it happens and what you can do to manage it.
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Jeff Kahn, M.S., Rise Science Co-Founder
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Woman feeling drowsy when she wakes up possibly due to sleep intertia

PSA: It's natural to feel like crap when you wake up. Contrary to ads for sleep aids (cue melatonin supplements), mattress companies, and bed sheet makers, that intense urge to go back to sleep is part and parcel of your sleep cycle. So is the drowsiness that lasts for 1-2 hours before you start feeling human.

The reason? Our bodies undergo sleep inertia when we rise from slumber.

Unfortunately, we crave to be at our best when waking up to meet life's 1,001 demands. The million-dollar question then is: How do you manage sleep inertia to get the most out of your morning routine?

Below, we’ll dive into the causes of sleep inertia and its unwanted effects on daily life. Last but not least, we will show you simple yet effective countermeasures you can use to manage sleep inertia successfully.

So, What Is Sleep Inertia?

Sleep inertia is characterized by a temporary period of sleepiness and poor cognitive performance from the moment you wake up.

Morning sleep inertia is an inevitable part of your sleep cycle as you transition from sleep to wakefulness. It may take up to 90 minutes for the grogginess to dissipate. In RISE, we call this transitional state your “grogginess zone.”

But, wake-up grogginess isn’t just limited to rise and shine. In fact, sleep inertia can also occur after a nap. Think of it as a phenomenon that happens any time your head hits the pillow, afternoon naps included.

Adenosine (a sleep-promoting chemical in your brain) is the main reason why your body needs some time to acclimate. It builds up during the day to induce drowsiness, creating what’s known as sleep pressure, so you nod off at night.

When you sleep, your brain purges adenosine from your body. But, this organic compound does take a while to burn off. Traces of it still remain by the time you wake up, inciting sleep inertia.

Since your brain is slowly awakening, it's normal not to feel your best mentally, emotionally, and physically during this time of day.

How to Tell If You're Battling Sleep Inertia

Key symptoms of sleep inertia usually manifest as:

  • Sleepiness (an urge to go back to sleep)
  • Disorientation or a serious case of "foggy brain"
  • Impaired cognition

In its more severe form, sleep inertia is called sleep drunkenness. You may experience:

  • Confusion
  • Slowness
  • Lack of coordination

Sleep drunkenness can last up to four hours, incurring debilitating consequences for the individual.

Why Do We Experience Sleep Inertia?

Sleep inertia: Anatomy of the brain

As wake-up grogginess doesn't seem to benefit us — think lower productivity and poorer cognition — why do we experience it then?

Sleep inertia may be a protective mechanism to ward off unwanted sleep intrusions while in slumber. This helps you fall back to sleep if you wake up in the middle of the night to use the bathroom.

Upon waking, you become instantly conscious, but the rest of your brain is still playing catch-up.

Picture this: Cerebral blood flow quickly returns to the brainstem (medulla oblongata) and thalamus to spark conscious awareness. Meanwhile, blood flow reaches the anterior cortex (in the limbic lobe) and prefrontal cortex (in the frontal lobe) more slowly. In human-speak, that means higher cognitive processes, such as your performance and decision-making skills, need more time to reach full capacity.

6 Culprits of Sleep Inertia — You’ve Probably Never Heard of  No. 1

Sleep inertia: A woman reaches to turn off her alarm clock

From sleep deprivation to chronotypes, several factors contribute to sleep inertia. Under certain circumstances, they may even intensify wake-up grogginess.

1. High Sleep Debt

Sleep debt — the amount of sleep you've owed your body over the past 14 days — is one of the main culprits of sleep inertia.

High sleep debt (due to prior sleep loss) intensifies and prolongs grogginess. Chronic sleep debt further worsens it.

The bottom line here is to get enough sleep to protect you from the crippling effects of sleep inertia.

Note: Even if your sleep debt is low, you're still prone to grogginess, albeit less intense.

2. Slow-Wave Sleep (SWS)

Slow-wave sleep is also called deep sleep and non-REM (rapid eye movement) sleep. This is when your brain initiates body repair and regeneration. During SWS, cerebral blood volume decreases, so cerebrospinal fluid can enter to flush out toxic, memory-impairing proteins.

Unfortunately, an abrupt awakening during SWS leads to a 41% impairment in performance — precisely what you don't need when waking up.

3. Recovery Sleep

Ever slept in after staying up too late the night before? That's recovery sleep for you. While it's a great way to pay down your sleep debt, science shows recovery sleep can aggravate sleep inertia and its symptoms.

Here's how:

  • Sleep deprivation increases sleep pressure, and causes you to spend more time in slow-wave sleep.This is your brain trying to self-regulate the higher-than-normal adenosine levels. Translation: The odds of your alarm clock ringing during SWS just got higher.
  • High sleep debt equals higher-than-normal adenosine levels, which may not fully disperse by the time you get up, deepening sleep inertia.

4. Chronotype

In the realm of chronobiology (the study of biological rhythms), your circadian rhythm determines your chronotype, which affects your natural sleep patterns and how fast you recover from wake-up grogginess.

In case you don’t know, your chronotype refers to your circadian preference for sleeping and waking at certain times of day. It’s a function of our genetics, and it’s why some of us are morning larks, others are night owls, and the rest are somewhere in between.

Research suggests later chronotypes may need a longer recovery time from sleep inertia than early risers. If you're a night owl who has to wake up in the early morning, give yourself a little wiggle room to get your brain up to speed.

5. Long Naps

Naps can be great for lowering sleep debt. But the longer the nap, the more likely you are to experience sleep inertia when waking up.

Long naps of 30 minutes and above usually lead to sleep inertia. On the other hand, short naps of 10-20 minutes tend not to result in grogginess (provided that you aren't particularly sleep-deprived in the first place).

6. Core Body Temperature

During slumber, your core body temperature naturally drops as a result of the sleep cycle. It's lowest during the deeper sleep stages and slowly rises back up before you get up. As such, waking up during this temperature trough may exacerbate sleepiness, too.

The Unwanted Effects of Sleep Inertia

Sleep inertia does a number on your productivity and performance through:

  • Poorer decision-making: Science warns that your decision-making performance drops 51% during the first 30 minutes of waking up.
  • Reducing reaction time: Yes, sleep inertia impairs your cognition in general. But, it also has a greater effect on your alertness and speed, leading to slower reaction times.
  • Inciting negative feelings: Most of us often feel cranky during the grogginess zone. On a more severe level, a large study involving 13,057 participants indicated a strong association between sleep drunkenness, bipolarism, and anxiety. 

These undesirable effects of sleep inertia aren't just limited to you as an individual. Lost sales, damages, accidents, and even deaths are just the tip of the iceberg when it comes to wake-up grogginess.

7 Countermeasures to Mindfully Minimize Sleep Inertia

It's not all doom and gloom, though. You can’t escape sleep inertia, but you can manage its downsides with simple tweaks to your daily routine.

1. Pay Down Sleep Debt

Since high sleep debt worsens sleep inertia, it's only common sense to keep your sleep debt as low as possible. Meeting your sleep need gives your body the time it needs to complete the nightly adenosine flush. This way, grogginess doesn't hold as much sway over you come morning.

In the RISE app, your sleep debt shows how you're doing on a nightly basis. To lessen morning sleep inertia, aim for five hours or less of sleep debt.

2. Play to Your Auditory Senses

We get it, there's nothing more annoying than the sound of your alarm going off. But, new research shows if you switch the usual beep to your favorite melody, it can help lessen sleep inertia.

3. Indulge In Caffeine

RISE app screenshot of the Limit Caffeine reminder

If you've been relying on coffee (or tea) to jolt you out of grogginess, you're on the right track.

Caffeine counters drowsiness-inducing adenosine to boost your alertness. But, do note that caffeine stays in your system for up to 10 hours.

RISE can help you track when you should stop drinking your cup of joe. Simply go to Habits and add the Limit Caffeine reminder to your schedule.

4. Bask in Sunlight

Sunlight signals to your brain that it's time to wake up. Not only does it send visual cues to your master clock, but it also raises your core body temperature to shake off the last dregs of sleepiness.

At times when sunlight isn't available — say, you're a night shift worker — try artificial dawn light. An example would be an alarm clock that uses gradually increasing light to mimic the sunrise. Its alerting effects help simulate the natural sleep cycle, so you feel less groggy when you awake.

5. Nap Strategically

If you didn't meet your sleep need (or if you did but still feel tired), get some shut-eye during your afternoon dip. The trick is to be strategic about your napping duration.

Power naps of 25 minutes or shorter replenish your energy levels for an hour to two. Remember, short naps are less likely to incur grogginess, unless you have a high sleep debt to begin with.

Pro tip: Research shows caffeine consumption just before a short nap significantly downplays the effects of sleep inertia.

6. Get Your Heart Pumping

Morning exercise also helps minimize drowsiness:

  • It increases your core body temperature and banishes grogginess.
  • It releases cortisol and serotonin to promote alertness and wakefulness.
  • It boosts blood circulation and adds energy to your day.

Pro tip: Combine exercise with sunlight for a power duo — like a walk around the block or a backyard HIIT session.

7. Be Consistent

One way to keep sleep debt low and your energy schedule regular is to be consistent in your wake and sleep times. This helps you fall asleep faster, stay asleep, and wake up easier. 

Moreover, science explains your circadian rhythm directly modulates slow-wave sleep (SWS). Adhering to your internal clock means you’re less likely to wake up during the deeper sleep stages, which further dilutes the effects of sleep inertia.

2 Ways to Beat Sleep Inertia at Its Own Game

Besides minimizing morning grogginess, you can also work around it to get the most out of your morning routine.

1. Knock Out the Routine Stuff

Remember, your brain is wading through the chemical adenosine fog to reach the realm of full alertness. It won’t do you any favors to focus on tasks that need peak cognitive functioning right when you wake up.

Instead, you should:

  • Get household to-dos out of the way.
  • Get moving — endorphins are an added bonus to start your day on a feel-good note.
  • Plan your to-dos so you can go straight into action when your morning peak approaches.

If you do have important tasks in the morning, wake up at least 90 minutes beforehand so your brain has sufficient time to fully rouse.

2. Do the Challenging Stuff Later

RISE app screenshot of your energy peaks

Schedule tasks that require optimal brainpower during your morning and afternoon peaks.

RISE can help you identify your energy peaks so you know when you'll be at your best. In the Energy tab, you'll notice the exact timings with the option for reminders in Habits.

RISE Helps You Manage Sleep Inertia for the Better

Now that you know waking up feeling great is a sleep myth, it's time to embrace it. And by embracing it, we mean recognizing your drowsy period and formulating ways to tackle it.

Start with scientifically proven methods to downplay sleep inertia. Whether it's a morning cup of joe or a relaxing jog, experiment with what works best for you. Next, use your morning to get low-maintenance tasks out of the way, so it frees up your energy peaks for the ones that really matter.

RISE is here to help you make these changes more easily so you can manage sleep inertia for the better.

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Rise is the only app that unlocks the real-world benefits of better sleep.

Instead of just promising a better night, we use 100 years of sleep science to help you pay down sleep debt and take advantage of your circadian rhythm to be your best.

Over the past decade, we've helped professional athletes, startups, and Fortune 500s improve their sleep to measurably win more in the real-world scenarios that matter most.

Rise Science is backed by True Ventures, Freestyle Capital, and High Alpha; investors behind category winners Fitbit, Peloton, and Salesforce Marketing Cloud.
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