Uninterrupted Sleep

Sleep Inertia

How often do you wake up feeling refreshed and ready to take on the day? If it is not often enough, you may be suffering from a common sleep phenomenon called sleep inertia. Sleep inertia is when you wake up feeling groggy, having poor concentration and an inability to do daily tasks at an optimal capacity.

Feeling groggy

Groggy is when you haven’t had a good night’s sleep and feeling a little dazed and wondering what can you do to wake up feeling fresh.  Feeling groggy can be of a short period of time, from one minute to four hours, depending on the person. Most people get over feeling groggy and tired within a half hour upon arising. While in a state of sleep inertia, you tend to wander about a little dazed, wondering what you should do next in terms of getting ready for the day. Most people get over this feeling and it doesn’t affect their daily lives; however, some with long periods of sleep inertia cannot function for enough of a period of time that daily activities are impaired. You can be mildly impaired or severely impaired with this condition. Some things affected include math abilities and cognitive processing.

Why does sleep inertia happen?

Researchers have done studies looking at blood flow to the brain after sleeping. They found that, upon awakening, the brainstem and the thalamus—deeper structures of the brain—recover their awakened level of blood flow before other parts of the brain wake up. It takes about fifteen minutes for the anterior cortical (thinking) regions of the brain to begin to get a normal amount of blood supply similar to that which occurs during the day. The lack of blood flow to cortical areas of the brain responds to the time you experience sleep inertia.

What Causes Sleep Inertia?

Short Nap

It is more common after a person has had just a short nap. Most research studies have focused on the development of sleep inertia just after awakening after a short nap. On the other hand, people can suffer from severe sleep inertia, even when they have slept a regular 8 hour night of sleep. One thing that influences the developing of this disorder is the time during the sleep cycle in which you are forced awake.

Wrong Stage of Sleep

For example, if the alarm goes off while you are in a deep sleep, you will have it more severely and for a longer period of time when compared to people who waken during stage 1 or stage 2 of the sleep cycle.  Those in REM sleep upon wakening generally have milder episodes of sleep inertia than those awakened during non-REM sleep. If, however, you sleep a full 8 hours of sleep and were not sleep-deprived in the day or two prior, the sleep inertia state tends to be less than 30 minutes duration and is of a milder intensity. This gives you plenty of time to shower, dress, and eat breakfast before doing any taxing mental work.

Low Temperature

If you have awakened while your body temperature is still low from sleeping, your sleep inertia will be more intense as your body struggles to regain its body temperature. If you are in a position in which you are recovering from sleep deprivation of a few days ago, you will likely feel more groggy than you would if you had not had that period of sleep deprivation prior to your recovery sleep time. Recovery sleeping after sleep deprivation tends to be of the deep-sleep variety, with brain waves generally really slow.

How to Overcome Sleep Inertia

Overcoming this disorder can take minutes or even hours depending on the person. Even in a state of sleep inertia, you can develop a routine of getting a cup of coffee or taking a shower or doing some kind of exercise like stretching, all  of which can bring you more quickly out of the sleep inertia state. Doing something relatively mindless during this time poses no danger and people tend to do well, suffering no complications during their daily life.

Sleep inertia effects

There are a few times, however, when this disorder poses some risk to the person having it or to people around them. This includes the following times:

  • When you have become sleep deprived

    If you are sleep deprived or if someone has awakened you from a particularly deep phase of sleep, the degree of sleep inertia you feel can be fairly profound and last longer than your normal periods of sleep. You should learn to recognize when you are in a state of sleep inertia and make sure you are not doing anything too taxing before it dissipates. If you work in a job that requires a great deal of mental energy, try to take a power nap of at least one hour during the time prior to engaging in mentally taxing exercises. Try not to become sleep deprived by going to bed and getting up at the same time every day, getting a minimum of 7 hours of sleep during a single time period.

  • Driving while sleepy

    If you find you must get out of bed and get behind the wheel before your natural period of sleep deprivation has passed, you may be one of the many people who drive while drowsy in the morning. This can increase your risk of accidents or even falling asleep behind the wheel. Driving while being sleepy has been found to be just as dangerous as driving while intoxicated.

  • When you are called into action too soon

    Doctors, ambulance attendants, firefighters and other helping personnel are sometimes called to emergencies before they have fully awakened from sleep inertia. This can lead to potentially costly and dangerous mistakes that occur before they are mentally ready to take on the challenge that faces them.

While sleep inertia means you are less of a “morning person” that you would like to be, it is generally not terribly harmful and you will recover fully after a relatively short period of time.