You went to bed early, fell asleep quickly, and had a great night’s rest on your buckwheat pillow. But, after your alarm goes off, you feel groggy, confused, and entirely out of it.
How does this happen?
We assume that when we have a good night’s rest, we will wake up feeling refreshed and energized, ready to take on the day - but this isn’t always the case! This groggy state is referred to as sleep inertia.
Sleep inertia is a phenomenon that results in feelings of drowsiness, cognitive impairment, disorientation, and grogginess that occurs after waking, even after getting adequate sleep. According to the Sleep Foundation, it is more common in those with alternative sleep schedules like flight attendants, military personnel, and those who work shifts. The phenomenon typically lasts anywhere from 15 to 60 minutes however can last a few hours after waking.
It's not too concerning if you are a bit slow on a Sunday morning while you read the paper and sip your coffee. However, when people need to get up and drive to work or are required to make safety-related decisions at their job, sleep inertia is a serious health concern. When experiencing sleep inertia, drivers and workers increase their risk of work-related injuries, mistakes, and car accidents due to decreased reaction times and cognitive abilities.
Although it is more common in those who work shifts, it can happen to anyone – and has likely happened to you at least once. Sleep inertia symptoms include impaired memory, visual attention, cognitive abilities, feelings of grogginess, and a strong desire to fall back asleep. You may have witnessed this in someone else, too, like a partner or child who has just woken up and seems “out of it.”
Due to the seriousness of sleep inertia, researchers have tried to determine the cause to explain the phenomenon and consequently find ways to prevent it. The research has come up with three main theories. The first is an increase in delta waves. Some research has supported the hypothesis that a reduction in beta wave activity and an increase in delta wave activity in posterior areas upon awakening may result in sleep inertia symptoms. Delta waves are slow and most often seen during non-REM sleep stages. Sleep experts state that these waves typically increase after periods of sleep deprivation or a night of poor sleep. So, the sleep inertia phenomenon may occur when you awaken during a non-REM sleep stage, and your brain hasn’t had the opportunity to reduce these delta waves.
The second theory as to why this phenomenon occurs is that there is a reduction in blood flow in the brain. As you go through the sleep stages, blood flow changes, following specific patterns corresponding to each cycle. In some cases where a sleep disorder exists, blood flow levels don’t follow typical patterns. For example, chronic fatigue syndrome (CFS) is associated with a reduction in cerebral blood flow. Individuals with CFS exhibit similar symptoms as sleep inertia, and therefore it is hypothesized that sleep inertia may be caused by a decrease in cerebral blood flow upon waking.
The third theory is that it is caused by a high level of adenosine. The nucleic acid compound known as adenosine is found in the brain and plays a critical role in sleep and wakefulness. When you are sleeping, adenosine levels are higher, and when it’s time to wake up, these levels should be lower. One study came across this potential cause when examining the effect of caffeine on sleep inertia. In the study, 28 normal adults were given low-dose caffeine or a placebo during the last 66 hours of an 88-hour period of wakefulness. During the period of wakefulness, they were allowed seven 2-hour naps in which they were hooked up to polysomnographic recording. After abruptly awakening from a nap and after every two hours of wakefulness, their psychomotor vigilance performance was tested. The results found that sleep inertia was absent in the caffeine condition. The researchers concluded that caffeine effectively overcame sleep inertia and believed this was due to adenosine. Caffeine affects the central nervous system through antagonism of adenosine receptors meaning that it lowers levels of adenosine. The researchers concluded that “increased adenosine in the brain upon awakening may be the cause of sleep inertia.”
All of these theories need more research to be considered conclusive, and various theories aren’t too helpful when it comes to avoiding sleep inertia. Yet, sleep experts have some recommendations that may work if you find yourself experiencing excessive grogginess upon waking.
Preventing Sleep Inertia
Lifestyle changes and adjusting when and how long you sleep could help prevent sleep inertia. Some research suggests that napping could help. Short periods of sleep in the middle of the day that are no longer than 30 minutes could help you overcome feelings of grogginess and prevent sleep inertia from happening. Just be careful you don’t oversleep because naps longer than 30 minutes have been found to increase your risk of sleep inertia symptoms as well as make it more difficult to fall asleep at night. Flight attendants that need to be sharp and have a heightened awareness at all times are often permitted to take segmented naps of no more than 20 minutes to prevent sleep inertia. Although these regulations vary with each airline and country, sleep timing is often adjusted to account for this risk.
The study mentioned earlier found that caffeine intake can also prevent sleep inertia. So, having that cup of coffee in the morning will shake off those groggy feelings and make you feel more alert. It works by blocking adenosine receptors in the brain, which in turn boost wakefulness.
But, keep in mind that too much caffeine can have detrimental effects and negatively affect your sleep at night. On the other hand, a short nap combined with caffeine can help shift workers feel much more alert. In 2018, a study found that night shift workers were able to combat the effects of sleep inertia following a nap when they chewed caffeinated gum. In addition, the results of the study found that it only took 15 to 25 minutes of gum chewing to take effect.
Even when you have a cup of coffee in the morning, waking up abruptly and rushing out the door isn’t great. Waking up gently is much better for you and will reduce your risk of experiencing sleep inertia. If your morning alarm is loud and jarring, causing a sense of panic when you wake up – it’s time to change it. Consider a smart alarm that wakes you up gradually. Alarms connected to light will increase progressively light in your room until you wake up or can progressively increase in volume. Connecting to a watch or personal device will register when you are in a light state of sleep and wake you up then. After you are awake, give your body time to get going. Start slow with some light stretching or sitting in meditation on your meditation pillow.
Sleep experts also suggest monitoring your sleep cycles and keeping them in alignment with your circadian rhythm. You can keep your circadian rhythm in check by getting natural light in the day and restricting light at night. Artificial or blue light can impact circadian rhythm and disrupt sleep stages. Keep your bedroom dark with room darkening blinds and leave electronics out of the bedroom. Then, open the blinds and get some natural light when you wake up. A 2016 review found that a glimpse of the sunrise can help speed up the time it takes to feel fully alert after waking up.
You should also keep your bedroom as cool as possible. When your bedroom is too hot, it prevents your body from naturally cooling before sleep. Cooling is a natural process before sleep that results in fatigue. Use appropriate bedding and set the temperature accordingly.
Although there isn’t a great deal of research on them, there are additional tips like washing your face in cold water, listening to upbeat music, or exercising. And most importantly, you need to ensure you are getting enough sleep during the night. Follow a regular sleep schedule, use a suitable pillow like a buckwheat pillow, and avoid alcohol, big meals, smoking, or caffeine close to bedtime.
Although sleep inertia is not considered a diagnosable sleep disorder, it can be frustrating. If you notice that waking up has become hard to do or you are feeling groggy for prolonged periods, speak with your doctor. A doctor may recommend a sleep study or keeping a sleep journal to learn more about your sleep patterns and why this is happening. With a sleep study, you can rule out any sleep disorders like sleep apnea and make lifestyle changes to improve your quality of sleep and wakefulness.
We all have those days where we want to spend a little more time in bed, cozy under the covers, and it doesn’t mean we are experiencing sleep inertia. However, understanding sleep inertia and how it impacts your cognitive abilities is essential to keeping you and others safe. If you are ever feeling groggy or “out of it,” you should not drive a car or engage in any activity that could put you a risk. Instead, have a cup of coffee and spend some time meditating until you are alert and ready to start your day!
