4 reasons behind why you sometimes jolt awake as you're falling asleep.

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You brush your teeth, jump into bed, turn the lights out and drift off. Everything is peaceful. And then BAM. You feel like you’re falling off a tall cliff, or tripping, and you jolt wide awake. Not so pleasant after all.

In a study published in the Sleep Medicine Journal, scientists from the University of Bologna, found the jolts (also known as “sleep starts” and “hypnic jerks”) we experience during the night are associated with a rapid heartbeat, quickened breathing, sweat, and sometimes “a peculiar sensory feeling of ‘shock’ or ‘falling into the void”.

So why does it happen? There are a few reasons apparently.

1. Myoclonus.

Myoclonus is the spasmodic jerky contraction of groups of muscles and is one of the reasons you can suddenly be thrown out of sleep. 70 per cent of us experienced it, but sadly – no one really knows the exact reason behind it.

“We don’t really know why exactly they happen. We know that they do happen and we know that it is something that is not clinically significant. They don’t cause any issues. It does happen to some people more than others and it can happen to you more often in particular times in your life,” explains Dr Maree Barnes, from The Sleep Health Foundation.

“For example, in pregnancy limb movement can be more common but that may be due to the fact that women often don’t sleep as well when they’re pregnant, so they may be more aware of the leg movements.”

2. Sleep Apnoea.

Some people may experience a pause in their breathing during sleep which can cause them to wake up startled. The culprit? Sleep apnoea. Up to five of these starts a night is normal in adults, apparently. However, for people with central sleep apnoea (CSA), it can last longer and occur more frequently. People with sleep apnoea commonly snore, toss and turn and have sudden leg movements.

“For people who have sleep apnoea, their oxygen falls and then they're briefly roused from sleep so that they can reopen their airway. It might wake you up during the night and you can experience a jolt because of this. For others, this doesn't happen and they continue to sleep," Dr Barnes explains.

If this sounds like something you experience, it's recommended you see a doctor. (Post continues after gallery.)

3. Restless Leg Syndrome (RLS.)

RLS is a problem where you feel significant discomfort in your limbs. It tends to affect the legs much more than the arms and it often happens if you're sitting down for long periods of time. You'll know if you have it, because you will experience a sudden urge to move the effected limbs.

RLS is always worse in the evenings and once asleep, people who experience it can wake up during the night because of it and experience a sudden jump when they do.

“Twitching jolt movements as you go off to sleep can be associated with RLS, often it can happen when you are moving though to a different stage of sleep,” Dr Barnes says.

4. Periodic Limb Movements of Sleep (PLMS)

As many as 80 per cent of people with Restless Legs Syndrome also have PLMS. It's when your legs or arms frequently and involuntary move when you're asleep. PLMS is mainly seen in the first third of the night, during the deepest type of sleep. Like with RLS, the twitching and moving of our limbs can wake us up during the night quite suddenly.

“In some cases PLMS can disrupt the sleep of the person or that of their bed partner. For others, PLMS isn’t a problem. If you’re waking up during the night from it, it can be a significant sleep disorder," Dr Barnes says.

What you can do about it.

What we do during the day can have a large effect on our sleep jolts. Certain habits can mean that we're more likely to wake up from external disturbances.

“There are things people do that can make it more likely that they will wake up when it happens. For example, if you have caffeine before you go to bed, if you exercise close to your bedtime. Also other factors like alcohol, nicotine, and stress can affect your quality of sleep," Dr Barnes explains.

“If the jerks are interrupting sleep, you need to look at all the things you do before bed and make sure you’re doing the right things. The best place to begin is the Sleep Health Website," Dr Barnes says.

If you're concerned about your sleeping patterns, see your GP to discuss some future strategies for you.

Do you experience jolts in your sleep? What are your tips for managing them?