“What’s With This Big Body Jerk Out of My Sleep?”

Tell me if this has ever happened to you.


You’re lying on your couch one night, watching a movie. An hour into the show, you gradually start to drowse. Your eyes are getting heavy; it’s increasingly hard for you to concentrate. You want to keep watching, but finally you start to give in: your eyes are closing.  A familiar, dark, fuzzy, comfortable sensation enshrouds you, mixed with a vague feeling like you’re falling into some kind of void. There is a brief reverie; you are asleep. Then, shortly thereafter and out of nowhere, BOOM! There’s a sudden shock-like sensation and an abrupt awakening. Your entire body jerks violently, like someone sucker-punched you, but there is no pain. That singular jerk almost sends you off the couch. The person you’ve been watching the movie with looks over, wondering what the hell is wrong with you.

Sound familiar? Most (up to 70%) of us have had that experience at one time or another in our lives. This phenomenon is called a hypnic jerk, or sleep start. Much is not understood about why or how it occurs, but a hypnic jerk consists of a single, sudden simultaneous contraction of multiple body muscles, basically the manifestation of a full-body reflex occurring shortly upon entering light stages of non-REM sleep and resulting in a sudden arousal from sleep.

Hypnic jerks tend to happen more in the setting of sleep deprivation or irregular sleep schedules. I vividly recall that during my residency training days, I abruptly awakened with these jerks all the time, probably because of the frequent sleep deprivation to which I was subjected at the time. It drove me nuts. Now that I’m allowed to get my 8 hours per night most of the time, only rarely now do they occur.

There are several reasons why it’s worth writing about hypnic jerks. First, some people freak out about them. The jerks in and of themselves generally are benign and aren’t harmful per se. Secondly, some may wonder if the jerks indicate an underlying medical problem, such as epilepsy. A generalized convulsion that involves jerking movements of the entire body are usually associated with repetitive jerking instead of a solitary body jerk, and you would be unconscious during the seizure. Finally, if the hypnic jerks are frequent or bothersome, there is often something that can be done about them. If you’re chronically sleep deprived, do what you can to gradually increase your total sleep time per night; most adults require about 7.5 – 8 hours of sleep per night. Regulate your sleep schedules by awakening around the same time every morning, including between workdays and non-workdays. Consider tapering down things that can disrupt sleep, like caffeine or alcohol. Sometimes stress or particularly strenuous activities late at night may also increase the likelihood of having hypnic jerks, so relaxing prior to your bedtime may be helpful as well.

Have a great weekend, everyone!

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