How to Stop Sleep Inertia

What is sleep inertia? How do we conquer it?

By Dr. Dan Gartenberg

Sleep inertia is the scientific term for what we commonly call the brain fog.  Sleep inertia is characterized by that grogginess you feel in the morning after you wake up. It is in part due to the brain functioning very differently than normal during sleep, especially deep sleep. The science has shown for example, that sleep inertia is worse if you wake up in a deeper stage of sleep. Brain fog occurs in the morning as the brain tries to replenish cerebral blood flow, it literally takes time for the blood to flow back into your brain in the morning. Anything that brings the brain activity to normal may reduce sleep inertia and help you feel more refreshed in the morning.

Sleep amount is one of the biggest factors that impacts sleep inertia. If you are getting a healthy amount of sleep then sleep inertia will usually fade after a half hour or so, otherwise, it can last as long as 2 hours. Waking up gradually is one of the best ways to reduce sleep inertia. There are a few simple ways to do this, such as with a smart alarm clock that fades in gradually. By starting an alarm almost imperceptible and ramping up, the body will awaken in a lighter sleep, when it is most ready to seize the day. Software like SleepSpace can also integrate with Smart Lights like LIFX bulbs in order to further promote this gradual wake up process.   The other benefit of a gradual alarm is that it helps you get extra sleep when you need it. This will also prevent that jolt feeling when you wake up by easing your body awake.

Ways to reduce brain fog:

  • • Waking up is a gradual process and by awakening gradually you can counteract this negative perception of brain fog.

  • • The adverse effects of brain fog on reaction time can be totally abolished by a moderately intense continuous noise.

  • • Countermeasures to brain fog including physical or mental exercise, external noise, bright light, caffeine, and splashing water on your face.

  • • Bright light reduces brain fog after napping.

For an in-depth understanding of sleep inertia check out this interview I gave on Quartz entitled, Brain fog explains why you feel so groggy when you wake up.


What if I'm getting enough sleep but I still experience sleep inertia?

Sometimes I see clients who are getting 8-9 hours of sleep, but are still experiencing intense morning brain fog. This could be a sign of poor sleep quality caused by an underlying condition like sleep apnea, hypersomnia, narcolepsy, restless leg syndrome (RLS) or medications and drugs that impact sleep quality. Sometimes this can also be cause by jet-lag and a misaligned circadian rhythm. If you believe that you may have an underlying condition, please consult your medical professional. Some solutions that can help anyone in the position include aligning your circadian rhythm with the right environmental cues called Zeitgebers

One more sleep inertia hack

Some of the science listed below has shown that temperature can also impact sleep inertia. When you wake up in the morning try splashing cold water on your face or taking a cold shower. This will activate your body's sympathetic nervous system which can counteract sleep inertia. 



Ferraro & De Gennaro, 2000. The sleep inertia phenomenon during the sleep-wake transition: theoretical and operational issues. Aviat Space Environ Med 71. pg. 843-848.

Kuboyama, T., Hori, A., Sato, T., Mikami, T., Yamaki, T., & Ueda, S. (1997). Changes in cerebral blood flow velocity in healthy young men during overnight sleep and while awake. Electroencephalography and Clinical Neurophysiology 102, 125-131.

Tassi, P & Muet, A. 2000. Sleep Inertia. Sleep Medicine Reviews, 4, 4, 341-353.

Tassi P, Nicolas A, Dewasmes G et al (1992). Effects of noise on sleep inertia as a function of circadian placement of a one-hour nap. Percept Motor Skills, 75: 291-302.

Hajak, G., Klingelhofer, J., Schulz-Varszegi, M., Matzander, G., Sander, D., Conrad, B., & Ruther, E (1994). Relationship between cerebral blood flow velocities and cerebral electrical activity in sleep. Sleep 17, pg. 11-19.

Hayashi, M., Masuda, A., & Hori, T. (2003). The alerting effects of caffeine, bright light and face washing after a short daytime nap. Clinical Neurophysiology 114, 2268-2278.

Baulk, S., Reyner, L., & Horne, J. (2001) Driver sleepiness-evaluation of reaction time measurement as a secondary task. Sleep, 24, 695-698.

Rupp, T., Arnedt, T., Acebo, C., & Carskadon, M. (2004). Performance on a dual driving simulation and subtraction task following sleep restriction. Perceptual and Motor Skills, 99, 739-753.