Ever get a falling feeling or jerks on drifting off to sleep?
Have you noticed a jump or involuntary twitch just as you are drifting off to sleep? A sense of falling? Do these wake you or disturb your partner? These are hypnic jerks, sometimes called sleep starts or sleep twitches and are a normal part of the process of transitioning from wake to sleep. Whilst some people can find them disturbing and even find they prevent them from getting in to deeper sleep, for most people hypnic jerks are just something they are aware of from time to time.
Why do hypnic jerks occur?
As part of the process of transitioning from full wake to full sleep, there is a change in muscular control and consciousness. During full wakefulness, you are full conscious and have active control of all your muscles. In contrast, in full sleep, you are not aware of your surroundings and muscles are partially relaxed. However, between full wake and full sleep, there is a period of transition that can last up to minutes. During this period of transition, with switching from active muscle control to more-relaxed muscle control during sleep, there can be unmasking of a spinal cord reflex that triggers jerking movements.
All of us have a spinal cord reflex that causes twitching movements, particularly in the legs every 20 to 40 seconds. However, we do not generally do this during sleep because of a signal from the brain down the spinal cord that suppresses movements. However, until full sleep is established, this suppressing signal is at full strength and the jerking movements stimulated by this spinal cord reflex can occur. With the loss of muscle activity or tone that is part of transitioning to sleep, we can also get a sense of falling.
You may have heard the expression of running around ‘like a chook with its head cut off’. This is a good example of this principle, as chickens, like humans, have spinal cord reflexes that enable active movements without having to have them initiated from the brain. In the absence of the brain controlling these spinal cord reflexes, there can be involuntary movements such as jerks, such as hypnic jerks. Think of them as your body behaving transiently ‘like a chook with its head cut off’ as the brain is neither consciously controlling muscle movements (full wake) nor fully suppressing muscle movements (full sleep).
Do I have a problem if I get hypnic jerks?
Hypnic jerks are a normal part of the process of transitioning from wake to full sleep. Some people get them more prominently than others so whilst most people will get hypnic jerks at some point, they can be particularly vigorous in some people and disturb their or their partner’s sleep.
Once people are conscious of hypnic jerks, they may develop a heightened awareness of them. In the clinic I often see people who have been having trouble with sleep and find that they can’t get to sleep, as each time they drift off to sleep they experience hypnic jerks that make them fully wake up again. When this happens it can lead to insomnia, and should be a trigger for you to talk to your doctor about your hypnic jerks and your sleep.
How are hypnic jerks treated?
Most of the time, hypnic jerks don’t need to be treated, as they are a normal part of sleep. But if they are disturbing you or your partner, there are a number of things that can help:
- Non-drug strategies: I use a psychology-based approached to reduce the focus on leg movements and prevent the escalating cycle of increased worry about falling asleep. I will generally use techniques borrowed from cognitive and behavioural therapy towards insomnia, particularly relaxation strategies and cognitive therapy as well as the principles of sleep restriction to make people sleepier when it is time to go to bed so they will more-quickly transition from wakefulness to sleep, spending less time in that transitional period where hypnic jerks can occur.
- Sleep study: Although having a sleep study is not a treatment, recording what is happening with muscles and breathing during the transition from wake to sleep can help people to better understand what is happening. It also allows me to ensure there are not other things contributing to hypnic jerks such as sleep apnea, and differentiate them from other movements during sleep such as periodic limb movements.
- Medication: If hypnic jerks are really interfering with people getting to sleep, I may use sleep-promoting medications for a short period of time to push people through the transition from wake to sleep. This can break a cycle where people become very aware of and sensitive to hypnic jerks and can help them get back into a better pattern of falling into sleep. My personal preference is to use short-acting medications that are best at getting people to sleep such as benzodiazepine receptor agonists or benzodiazepines. (More on these medications here.)
What should I do if I’m troubled by hypnic jerks?
If hypnic jerks are causing problems for yourself or your partner, it is important to talk to your health professional. It may be that the hypnic jerks are either much more exaggerated than normal or are being made more frequent or more prominent by another problem such as a sleep disorder.
When I am referred someone with prominent hypnic jerks that are disturbing their sleep or their partner’s sleep, I will normally evaluate them with a comprehensive clinical evaluation to look for other medical factors, medications or other conditions that may be causing increased hypnic jerks. I will also arrange to do an overnight sleep study (see video – ‘Having a sleep study’) to look at what is actually happening with leg movements around sleep onset, look at how the brain reacts when leg movements do occur, and ensure other sleep disorders are not contributing to hypnic jerks or sleep disturbance.
Related posts & links:
- Periodic limb movements
- Having a sleep study
- Medication for insomnia
- Cognitive behavioural therapy for insomnia
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