Have you ever been lying there, or lying next to someone, and there was a sudden jerk or twitch? And they seem to happen all through the night without anyone waking up or experiencing some sort of crazy dream? 

These are called hypnic jerks, or sleep starts. They are involuntary muscle contractions that you may experience during the night, sort of like a muscle twitch. Hypnic jerks are referred to as a type of myoclonus, and is the equivalent of a hiccup, or rapid, involuntary muscle movements. Hypnic is short for hypnagogic, which means the transition from wakefulness to sleep which is when these twitches occur.  

What do they feel like? 

Hypnic jerks seems to occur randomly as you're falling asleep, and only affect one side of the body. For example, your left arm and left leg may be the only things that twitch. You can experience a single jerk, or in multiple successions before your body relaxes again. 

Your body is not the only thing that moves, however. You can also experience other sensations or mental imagery along with the jerk, like a dream or hallucination. Similar to when you fall asleep and have a dream that you're falling and jerk to keep yourself from hitting the ground. Hypnic jerks aren't painful, but some people can experience a tingling or painful sensation.  

Hypnic jerks do not feel the same all the time. Sometimes they are strong enough to jolt someone awake and disrupt the process of falling asleep. Other times, they are so mild that the person to whom they're happening doesn't even notice. However, their sleep partner might, which can cause concern.

Hypnic jerks happen at any age, but are more common in adults. It may be due to certain causes like caffeine and elevated stress, which are more common in adulthood. 

The causes of hypnic jerks 

The causes of hypnic jerks are unclear, but there are a few theories. Hypnic jerks and other types of myoclonus are activated by the part of your brain that is in control of your startle response. When you fall asleep, it is proposed that this part of the brain misfires, and creates a reaction that leads to a hypnic jerk. 

There are also certain risk factors that may increase the likelihood of you experiencing a hypnic jerk. This can include excessive caffeine and stimulant use, vigorous exercise before sleep, and emotional stress and sleep deprivation. 

Stimulants like caffeine and nicotine activate your brain, and can stay in your system for several hours, leading to disrupted sleep. Even drinking coffee six hours before bed can still lead to trouble falling asleep. Consuming these substances too close to bedtime can trigger hypnic jerks. 

Vigorous exercise is great, but too close to bedtime can have a similar effect to caffeine. There is an overstimulation of the brain that can leave you feeling more alert than tired. Therefore, exercising too late in the evening can lead to hypnic jerks. 

Sleep deprivation, caused by insomnia or a poor night's sleep, can lead to unwanted side effects; hypnic jerks included. Stress and anxiety, which also can lead to sleep deprivation, can increase your risk of developing hypnic jerks. When you are stressed or anxious, your cortisol levels remain high during sleep. Anxious thoughts can make it more challenging to fall asleep, and can lead to more jerks in the transition between wakefulness and sleep.

Are hypnic jerks dangerous? 

Hypnic jerks are not dangerous, and in fact, cause very little disruption to the sleeper. The same may not be said for your sleep partner who could be experiencing frequent disruptions every time you jerk, but up to 70% of sleepers experience them. A particularly violent jerk could lead to a minor injury, however that is not common. 

In most cases, seeing a doctor for hypnic jerks is not necessary. If you only experience them when you are falling asleep, then there is minimal harm or danger. However, if you are experiencing multiple, persistent twitches during the daytime, then this could be a different type of myoclonus, not a hypnic jerk. In this case, those muscle contractions could indicate a different disorder like epilepsy, nervous system disorders, a head or spinal cord injury or organ failure. 

Periodic limb movement disorder is also another condition in which the symptoms are similar. If you are experiencing severe sleep deprivation and think they may be due to PLMD, then it's important to speak with your doctor to prevent worsened sleep deprivation. 

Preventing Hypnic Jerks 

Hypnic jerks are a normal part of sleep,s o it's unlikely with any intervention that you are going to actually remove them completely. However, you can reduce their intensity and frequency, while also improve both your sleep and your partners'.

One way to improve your sleep is to develop better habits. Improving your sleep hygiene makes it so much easier for you to get consistent sleep. This could reduce the occurrence of hypnic jerks. Improving your sleep behavior is not the easiest thing, but with a stepwise process, you could definitely make some beneficial steps forward. 

One way is to go to bed and wake up at the same time everyday, including the weekends. Make sure your bedroom is cold, dark and quiet. Reduce your electronic use at least an hour before bed. And follow the same night time routine everyday. This trains your brain and body to go to bed. 

In addition to improving your sleep behaviors, also reduce some of the risk factors for developing hypnic jerks. This includes continuing to exercise, but make sure to leave two hours between finishing your work out and going to bed. By doing this, you give your body a chance to cool down. Also, reduce your caffeine consumption and nicotine use. The early afternoon is a good cut off for your last cup of coffee. Avoid nicotine and alcohol altogether. They not only disrupt sleep, but are also not good for you. 

If you make these changes and your sleep is still severely interrupted, then please click the orange button below to take a free online sleep test and talk with one of our sleep health professionals.

https://www.sleepfoundation.org/parasomnias/hypnic-jerks