Sleep Inertia = Grogginess

Pietari Nurmi
Jul 15 · 3 min read

Do you wake up often groggy, without any sense of time or place? You can't seem to think straight, movements are stiff, and you feel like you were stunned. Scientists call this phenomenon sleep inertia, but essentially it is the same as morning grogginess. After waking up, your motor and cognitive abilities are temporarily weakened. During sleep inertia, your senses are impaired, and focusing your thoughts is challenging.

Sleep inertia is perfectly normal. The level of grogginess can vary greatly, but everyone experiences it in some form or another after waking up. The effect is strongest immediately after waking up, and the symptoms fade away, usually in 15-60 minutes. Sometimes it can pass in minutes, but in some situations, grogginess might last for several hours even. Two main factors affect the intensity of sleep inertia:

  1. Sleeping too little (or having sleep debt that has not been slept off)

  2. Waking up during a nonoptimal stage of the sleep cycle (during deep sleep)

If you feel groggy almost every morning and the effects don't pass quickly, there is definitely something you should change in your sleeping behavior. Take a good look at the rest of the lessons this week and consider the possible reasons behind your grogginess. During the week, we will look into the root of what makes waking up difficult in the morning.

Additional Reading

Hilditch, C. J., Dorrian, J., & Banks, S. (2016). Time to wake up: Reactive countermeasures to sleep inertia. Industrial Health, 54(6), 528–541.

Tassi, P., & Muzet, A. (2000). Sleep inertia. Sleep Medicine Reviews, 4(4), 341–353.