Understanding Sleep Inertia: Symptoms and Effects

In a perfect world, you’d wake up every morning feeling refreshed, energized, and ready to start your day. In the real world, however, waking up is often accompanied by a feeling of grogginess or heaviness that can take you hours to shake off.

The medical name for this early morning slump is sleep inertia.

Experts define sleep inertia as a form of cognitive performance impairment that decreases over time and can be affected by factors like sleep loss and the time of awakening.

If you feel disoriented as soon as you wake up or desire to fall back asleep, you might be suffering from sleep inertia. This article looks at the most common sleep inertia symptoms and ways to break through it.

What is Sleep Inertia?

When your body suffers a temporary impairment of cognitive and sensory-motor performance immediately after waking, it is a sign of sleep inertia. It involves a feeling of drowsiness and reduced motor dexterity and typically lasts up to half an hour, though some people experience it for several hours.

By using this definition, sleep inertia can be differentiated from simply having a one-off bad night’s sleep and suffering through the after-effects.

Although sleep inertia is not usually a cause for concern, it can be a serious matter for people who need to be fully alert soon after waking up — truck drivers and operators of heavy machinery, for example — as any lapse in concentration could have dire consequences.

Sleep Inertia Symptoms

The primary sleep inertia symptoms are feelings of grogginess or heaviness upon awakening and a reduced ability to concentrate or perform physical tasks. These symptoms are usually felt most profoundly within 30 minutes after waking, but they may linger for several hours. Additionally, it can be present upon waking up from a long nap (over 30 minutes).

Common symptoms of sleep inertia include:

• Impaired spatial memory
• An desire to fall back asleep
• Grogginess
• Impaired visual attention
• Impaired cognitive ability

Sleep Inertia in Teens

Teenagers are more likely to suffer from sleep inertia than other age demographics. A 2014 study of almost 7,000 adolescents in Portugal found that 90.6% of teens had difficulty waking up and 64.7% experienced “daytime sleepiness.” [1]

Sleep trouble among teens is partly caused by changes to their circadian rhythm during puberty. Because of these changes, teens will naturally fall asleep later, but they are typically still required to wake up early to get ready for school.

This results in a mismatch between sleeping and waking time — a phenomenon called delayed sleep-wake phase syndrome (DSPS) — that can contribute to sleep inertia.

Of course, teens don’t always help themselves. Keeping irregular hours for social or leisure reasons, such as partying or playing video games all night, can also contribute to sleep inertia.

Sleep Inertia Cures

Some sleep inertia cures are preventative and can be enacted before going to bed, while others are reactive and can be deployed as an emergency quick fix.

Fix your sleep schedule

Methodically planning your sleeping hours is an effective way to prevent sleep inertia. If possible, try to accommodate your body’s natural circadian rhythm and sleep during hours of darkness rather than staying up late into the night. Keeping a consistent sleep schedule also results in better sleep.

Unfortunately, this preventative sleep inertia cure may not be feasible for everyone. For instance, people who work night shifts need to sleep “unnatural” hours.

Regulate Your Body Temperature During Sleep

Staying cool during the night promotes healthy sleep. But there is also a more direct link between body temperature — particularly the temperature of the hands and feet — and sleep inertia.

A 2004 study hypothesizes that manipulating the temperature of the body’s extremities through cooling strategies may result in faster sleep inertia dissipation due to a “functional relationship” between sleepiness and blood vessel dilation in the hands and feet. [2]

Let the Light In

Before you shut those blackout blinds, consider whether a bit of morning sun could reduce your sleep inertia.

Some scientists argue that gradual exposure to morning light can reduce the feeling of tiredness upon waking up by triggering the brain’s cortisol awakening response (CAR). If your bedroom doesn’t get morning light, try using a sunrise alarm clock with simulated sunrise lighting instead.

Brew up in the Morning

If you’ve woken up with sleep inertia, one of the easiest reactive cures is drinking coffee or another caffeinated drink. Caffeine blocks adenosine receptors in the brain, resulting in increased alertness.

That being said, people suffering from sleep problems shouldn’t consume caffeine too liberally. Having a cup of coffee late in the day can contribute to difficulty sleeping and exacerbate sleep inertia the following day.

Take a Cold Shower

Although less enjoyable than a hot cup of coffee, taking a cold shower can give you a rapid burst of energy and knock away the symptoms of sleep inertia.

Cold showers also have other health benefits such as increasing blood circulation and soothing sore muscles.

Nap strategically

Another means of countering post-wakeup sleepiness is… sleeping. Having a short nap can offer benefits, including helping reduce the physical and mental fatigue associated with sleep inertia.

Be sure to set the alarm though, or you might suffer from another bout of sleep inertia after nap time. Naps should last less than 30 minutes before the body has time to enter slow-wave sleep, which is harder to wake up from.

Read More: We've got the answer if you have been asking yourself, "How long should I Nap?

Final Thought

Is sleep inertia normal? Yes, but that doesn’t mean you need to suffer through it for several hours a day. By implementing preventative strategies like regular sleep times and a regulated sleep temperature, in addition to remedial measures like coffee and napping, it is possible to reduce those feelings of morning grogginess significantly.

Learn how our water-based cooling technology can help regulate your body temperature for better, deeper sleep and reduce the risk of sleep inertia upon waking.