What is sleep Inertia?

What is sleep Inertia?

Have you ever woken up on a morning and felt really groggy? If so, it’s likely you have been experiencing sleep inertia. This is when we are awake but our body is still in a sleeping state, including parts of our brain. This can make the simplest of tasks difficult, for example: brushing your teeth, making a cup of tea or packing a bag for school or work.

The brainstem arousal system is the part of the brain responsible for your physical functioning and is in charge of telling you how to do a job – like eating your breakfast or turning on the shower. However, our prefrontal cortex (PFC), which looks after decision-making and self control takes some time to warm up, making the first tasks of our day feel weird and unnatural.

Sleep inertia lasts between 15 and 30 minutes; but in some people may last up to four hours if sleep deprived! If you are one of those people who survive each morning on a 20 minute dash out the door, perhaps you should reevaluate your morning routine to give you some time to properly wake up before heading out. If you drive to work, beware of sleep inertia as research suggests that almost 20% of accidents on major roads are sleep-related. Like mentioned earlier our PFC takes time to warm up on a morning, meaning our reaction time and decision-making isn’t up to speed – this could prove costly for early rush hour drivers.

There are several ways to reduce the effects of sleep inertia, the most obvious is of course being well-rested. Getting enough sleep on a night is important to starting your day right, the more rested you are the less groggy you’ll feel and for a shorter period of time.

Another approach is timing your morning alarm to the end of a sleep cycle and waking up at the same time everyday. A complete sleep cycle is approximately an hour and a half, so the ‘best’ time to wake up would be seven and a half or nine hours after you go to sleep. Humans are creatures of habit so waking up at the same time everyday will feel more natural reducing the effects of inertia. Waking up in the middle of a cycle is likely to disrupt rapid-eye-movement (REM) sleep, which can makes us feel sleepy as we still have high levels of melatonin in this stage of sleep.

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