Why Do We Experience Sleep Inertia After Waking Up Abruptly?

It’s early morning and the alarm rings, abruptly yanking us from our blissful state of sleep. In those few moments after awakening from sleep, we feel groggy and, without a doubt, grumpy.

grumpy cat

What you may not know though, is that our brains don’t function at full capacity for at least the next 30 minutes after abruptly waking up. In some cases, this lasts for up to 4 hours after our nasty awakening (brought on by that hated alarm).

Now, let’s take a look at why this happens and how it affects us – beyond being labeled “not a morning person”.

Sleep Inertia

Many of you who wake up early to go to your schools, colleges or offices often notice this effect. By now, you’ll be used to it and don’t think twice about jumping out of bed at the sound of the alarm, but the truth is, this abrupt arousal makes you want to go back to sleep and prevents you from being fully attentive to what you’re doing. This is not normal! Known as Sleep Inertia, this mental state we find ourselves in just after waking up abruptly is mainly due to the fact that our external alarms (either in your phone or if you’re truly old-fashioned, an actual alarm clock) are not synced up with our internal alarms (regulated by our circadian rhythms, the body’s internal time-keeping mechanism).

Man Inside Clock


What Happens Inside The Brain

The moment that we wake up, there’s a part of our brain that is instantly activated. These are the arousal systems in the brain stem. They give us a sense of wakefulness and mobilize our body. Essentially, we are awake and ready to move. However, the part of the brain that isn’t fully activated after waking up is the cortical region. This region is responsible for a person’s attention, perception, awareness etc. A major part of this region is the prefrontal cortex, which is the area most affected by disrupted sleep patterns. The prefrontal cortex is involved in our decision-making and our self-control, so there’s no surprise that sleep inertia results in our inability to properly apply toothpaste to our brush.

sleep deprived

Social Jetlag

“Social Jetlag” is a term coined by a professor of chronobiology (which is the study of biological rhythms or cycles) at a German university, Till Roenneberg. It basically refers to the difference in our actual wake-up time and the time we should be waking up, as dictated naturally by our bodies. This social jetlag can be extreme (over 2 hours) or mild (at least 1 hour).

This phenomenon is closely linked with the sleep hormone melatonin. People experiencing sleep inertia basically wake up while the hormone is still in play, which is what leads to our desire to go back to sleep when we are so rudely awoken.

How This Affects Us

This sleep inertia may not seem all that important, but the social jetlag that builds up over many months, or even years, eventually ends up having unexpectedly drastic health effects on us. Professor Roenneberg and a psychologist, Marc Wittmann, found that this social jetlag built up over a long time puts you at an increased risk of obesity. In fact, one hour of social jetlag corresponds to a 33% greater risk for obesity.

It was found that people with higher social jetlag are more likely to increase their consumption of alcohol, cigarettes and caffeine. This interesting phenomenon ties in with another interesting finding regarding people taking the night shift; it was found that these nocturnal individuals are also increasing their risk of cancer, heart disease, diabetes and other chronic diseases.

Another finding, which should particularly interest students, suggests that sleep inertia (which is mostly dependent on our sleep timings) had an effect on their performance during their exams.

exam inertia

Essentially, these people are going to sleep and waking up at times that aren’t particularly healthy, leading to sleep inertia and an eventual build-up of social jetlag.

Sleep Better

Fortunately, there’s some excellent news for those of you who regularly experience sleep inertia. Creative research, involving people sent off on a camping trip where their sleep cycles were governed solely by nature, found that sleep timings can be changed for the better within as little as a week.

Clock Sunshine


In other words,do you best to sleep better! As far as sleep inertia and social jetlag are concerned, you don’t necessarily need to sleep longer – just smarter. It’s time for you to win that battle against the evil alarm.


  1. Sleep Inertia – Wikipedia
  2. Morning Sleep Inertia in Alertness and Performance – CiteSeerX
  3. Are You Awake? Cognitive Performance And Reverie During The Hypnopompic State – University Information Technology Services (University of Arizona)
  4. Time To Wake Up: Reactive Countermeasures To Sleep Inertia – National Center for Biotechnology Information
The short URL of the present article is: http://sciabc.us/uRkv1c
Help us make this article better
About the Author

Brendan has a Bachelors of Science degree in Biotechnology from Mumbai University (India). He likes superheroes, and swears loyalty to members of the Justice League. He likes to take part in discussions regarding the human body, and when he is not doing that, he is generally reading superhero trivia.

Science ABC YouTube Videos

  1. Can Mutations Make Us Superheros?Can Mutations Make Us Superheros?
  2. Gravitational Lensing: What It Is And How It Is Helping Us Discover New GalaxiesGravitational Lensing: What It Is And How It Is Helping Us Discover New Galaxies
  3. What Exactly is Archimedes Principle: Explained in Simple WordsWhat Exactly is Archimedes Principle: Explained in Simple Words
  4. What is Evolution? A Simple and Brief ExplanationWhat is Evolution? A Simple and Brief Explanation
  5. What is the Heisenberg Uncertainty Principle: Explained in Simple WordsWhat is the Heisenberg Uncertainty Principle: Explained in Simple Words
  6. Why Are Planetary Orbits Elliptical?Why Are Planetary Orbits Elliptical?
  7. Why Are There Stones Along Railway Tracks?Why Are There Stones Along Railway Tracks?
  8. Why Do We Dance To Music?Why Do We Dance To Music?