Why can't you sleep when you know you have to wake up early

Is there actually anything worse than knowing you have to set your alarm super early in the morning, only to then find yourself lying awake for hours unable to actually fall asleep?

We'll wait.

In truth, there are worse things – like actual insomnia. But when it comes to dealing with a bit of a change to your sleeping routine, why does it feel like your brain or body can't actually switch off?

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Medical Review Expert at SleepFoundation.org, Dr. Abhinav Singh (MD, FAASM) says it's no surprise people struggle in this scenario as your mind is preoccupied.

"Thinking about something first thing in the morning, such as a flight, then going to sleep is the same as leaving a cake in the oven to bake and trying to sleep at the same time," Singh, who is also Medical Director of the Indiana Sleep Center, tells 9Honey.

"Your mind will always be preoccupied with that event and will have a hard time falling into sleep, and it likely will not reach deep states of restful sleep."

What is Deep sleep?

Once you fall asleep, your body cycles through four different sleep stages – three non rapid eye movement (NREM) phases of sleep, followed by one rapid eye movement (REM) sleep stage. It usually takes between 90 and 120 minutes to cycle through all four stages, after which the cycle starts again.

Deep sleep, also called slow-wave sleep, occurs in the third stage of non-rapid eye movement (NREM) sleep.

Typically you descend into deep sleep within an hour of falling asleep, but then experience progressively shorter periods as the night goes on.

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While all stages of sleep are necessary for good health, deep sleep offers specific physical and mental benefits.

Your body works to build and repair muscles, bones, and tissue, and immune system functioning. It's also important for cognitive function and memory.

Automatic body functions like breathing and heart rate are also very slow and your muscles are relaxed.

Most adults should aim for seven to nine hours of sleep each night, of which ideally between 13 per cent and 23 per cent should be spent in deep sleep.

So if you get seven hours of sleep each night, then you spend approximately 55 to 97 minutes each night in deep sleep.

Of course if you are lying awake for hours first, or tossing and turning throughout the night thinking about how soon you have to 'wake up', it's no surprise you don't hit that required deep sleep stage.

What can I do to help?

Because deep sleep is part of the memory formation process, you may struggle to consolidate memories after nights without enough deep sleep. Even after one night of insufficient sleep you may experience difficulty learning or remembering information.

Which is not ideal if the reason you are getting up early is something important.

So what can we do to help the situation? Singh has one tip.

"If such an event is taking place, then bank your sleep a couple nights before, by sleeping an hour or two extra each night," he suggests.

"Then the effect of the poor sleep the night prior doesn't feel as bad."