Sometimes we wake up feeling like our brain and body are still sleeping, and we are unable to think clearly or act right. We feel tired and groggy as soon as we open our eyes. This is called sleep inertia, and it happens when we wake up. Sleep inertia usually lasts up to thirty minutes. It happens because we were abruptly woken up when our body was not prepared for waking.
Many people struggle with sleep inertia – knowing more about why and how it happens can help its prevention. Respecting your sleep schedule and letting the morning light in the room are only two of many pieces of advice you can get if you fight this widespread problem.
Some refer to ‘sleep drunkenness’ when talking about sleep inertia.
When and why does sleep inertia happen?
It happens as soon as we wake up – while the blood flow in the brain is still lacking. This impairs our mental abilities – we are unable to focus, do simple addition, or remember things. It can be as bad as being unable to remember what day it is or who and where we are.
Sleep inertia can happen after a full night’s sleep or after a daytime nap. It is generally associated with being woken up abruptly from an incomplete sleep stage – especially deep sleep.
When we are in deep sleep, our bodies and brains are undergoing major maintenance – our memory is consolidated (from short-term memory into long-term memory) and cells and tissues are restored. At this time, we are almost completely unresponsive to what’s happening around us and are very difficult to wake up. Our body is designed so that we can’t be easily woken up from this important sleep stage, but when we actually are, we are completely disoriented and confused.
We can suffer from sleep inertia even after a nap – and this happens when our nap exceeds 20-30 minutes and we enter deep sleep, from which our alarm wakes us up. Then we tend to feel worse than we did before the nap. However, if you take a nap of about 90 minutes (the length of one sleep cycle), you are likely to wake up from REM or lighter sleep stages – which is perfectly fine.
The good news is that either short naps or those of about 90 minutes in the afternoon decrease the effects of sleep inertia if you’ve had one from the morning.
How long does sleep inertia last?
In most cases, it lasts for about 10-30 minutes. During this time your mind and body are adjusting to wakefulness.
However, it can last a lot longer, especially if you are sleep-deprived. This means you can go 2 to 4 hours with sleep inertia, or sometimes an entire day feeling disoriented or fatigued.
Some really bad ideas that aggravate sleep inertia
If you frequently suffer from sleep inertia, you are either doing something wrong (bad sleep habits) or have a sleep problem/disturbance. These are things you should avoid in order to ease the problem you have.
- You use the snooze button. It wrecks your circadian rhythm. Your body works best if you keep to a regular schedule – then it knows how to plan out the sleep stages. If you keep hitting snooze, you are not doing your brain and body a service because you are confusing the internal rhythm. Sleep time should be reserved for sleep and wakefulness for being awake. Anything in between will cost you the time, productivity and energy.
- You are sleep-deprived. Don’t cut back on sleep in the week and don’t try to make up for the lost sleep by sleeping in on the weekends. Sleep deprivation creates the groggy feeling and increases the chances for a headache and bad mood. Adenosine, a nerve cell activity product, builds up during the day and makes us sleepy. When you have enough sleep, the brain is completely cleared out from it – when this happens, you wake up happy and energetic. When you don’t sleep well, adenosine is still quite present and we wake up tired. Then we need caffeine to cover the effect of adenosine and trick us into thinking we have energy. The truth is, we’re still worn out and won’t truly get rid of sleep inertia.
- Your naps last for about 45-80 minutes. During this time, you are likely to experience deep sleep and waking up from it will have heavy sleep inertia as a consequence.
- Your room is too dark in the morning. If the room is completely dark, it means that the ‘wake-up’ center in your brain won’t receive any information about the morning arrival and will not begin preparing the body and mind for waking up. If an alarm abruptly wakes you up in a dark room, you are likely to be disoriented.
- Untreated sleep disorders. People who suffer from obstructive sleep apnea, restless leg syndrome, insomnia, and hypersomnolence disorders that affect sleep duration and quality are at a higher risk of having sleep inertia as well as excessive daytime sleepiness.
Sleep inertia shouldn’t be ignored. People who have important tasks early in the morning have to make sure that they have had enough sleep. Sleep inertia showed to be more impairing to our consciousness and reaction time than all-night sleep deprivation. Some authors compare it to be as bad as being legally drunk. Driving while still under the influence of sleep inertia can be lethal. Important decisions should not be made at this time.
What can you do to stop having sleep inertia?
The most frequently used quick fix for sleep inertia is coffee, because it instantly increases alertness and speeds up the process of fully awakening. However, as mentioned above, caffeine only masks the tiredness, and if you want to change your habits into more healthy ones and naturally get rid of sleep inertia, make sure you have healthy sleep.
- Stick to the same sleep-wake schedule every day.
- Let the morning light in, but make sure the room is dark at night – there is a significant effect of light on our sleep quality.
- Skip the snooze button.
- Have a short nap during the day.
- Keep the room temperature at about 65°F – this helps body temperature to decrease as the sleep time approaches. It also ensures good quality rest.
- Visit a doctor if your sleep inertia affects the quality of your life or work – especially if you fall asleep easily or at inappropriate moments.
If someone is naturally a morning person, they will probably not have sleep drunkenness. It mostly affects night owls, who also frequently complain of social jet lag. That means their chronotype (personal sleep-wake rhythm) is out of tune with how society works and it usually leads to chronic sleep deprivation.
All in all, remember that sleep inertia is a sign that something didn’t go right – either on the previous night or chronically, over a long period of time. You can decrease or completely solve this problem if you have sleep habits which ensure a good night’s sleep.
- Ritchie H. K, Burke T. M, et al. Impact of sleep inertia on visual selective attention for rare targets and the influence of chronotype. Journal of Sleep Research. https://www.ncbi.nlm.nih.gov/pubmed/28378363 Accessed January 18, 2018.
- Trotti L. M. Waking up is the hardest thing I do all day: Sleep inertia and sleep drunkenness. Sleep Medicine Reviews. https://www.ncbi.nlm.nih.gov/pubmed/27692973 Accessed January 18, 2018.
- Morning grogginess more debilitating than sleep deprivation, according to CU-Boulder study. EurekAlert! January 10, 2006. https://www.eurekalert.org/pub_releases/2006-01/uoca-mgm121905.php Accessed January 18, 2018.
- Hayashi M, Matsuura N, Ikeda H. Preparation for Awakening: Self-Awakening vs. Forced Awakening: Preparatory Hanges in the Pre-Awakening Period. International Review of Neurobiology. Volume 93, 2010, Pages 109-127.
https://www.sciencedirect.com/science/article/pii/S0074774210930055 Accessed January 18, 2018.
- Ferrara M, De Gennaro L. The sleep inertia phenomenon during the sleep-wake transition: Theoretical and operational issues. Aviation Space and Environmental Medicine. September 2000. https://www.researchgate.net/publication/12367344_The_sleep_inertia_phenomenon_during_the_sleep-wake_transition_Theoretical_and_operational_issues
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