What’s Happening When You “Jerk” Awake?

You’ve probably had that unfortunate moment in a dull workplace meeting: You’ve fallen asleep and you don’t even notice until you twitch awake with the sensation of falling. Your face probably turns red with embarrassment as others take note of your dozing off, but this sensation called the hypnic jerk is a common part of falling asleep. It may occur anywhere you start to drift off—whether you are sleeping in your cozy bed or struggling to stay awake as your boss drones on in the conference room. So why does your body seem to betray you just as you start to get comfortable and fall into deeper sleep?

The complex nuances of sleep

There is a lot that we don’t understand about sleep, but one thing that is known is that not all sleep is alike. As you snooze, you actually enter various sleep stages throughout the night. Hypnic jerks only occur in non-rapid eye movement (REM) sleep, and they tend to be more frequent in children than adults.

• External influences —A hypnic jerk could be related to an environmental influence that arouses a muscle twitch, but you will probably wake up without recognizing what the cause was. In fact, environmental stimuli are not really observed by sleeping individuals. If you were to sleep with your eyes held open (imagining you could fall asleep this way), pictures or images in front of you would not likely make their way into your dreams. This indicates that something else is going on internally to cause you to wake up.

• Links between dreams and movement —You might think that dreaming of falling will cause you to wake up feeling like you are falling down. However, the hypnic jerk occurs in a sleep state where you are not yet dreaming. In other words, you may find yourself moving as a result of other dreams (i.e. your legs move as you dream of running), but the hypnic jerk is a different sensation.

• Sleep’s on-off switch —The most likely cause of the hypnic jerk lies in the way your body prepares itself for sleep. Under normal conditions, you can’t fall asleep at a moment’s notice, because sleep is not just an on or off process. The body must surrender motor control as it enters sleep paralysis, and the hypnic jerk is what happens when there is a burst of lingering energy that needs to get out.

Control over hypnic jerks

While you cannot fully take control of the complex processes that happen in the brain to allow the body to sleep, you might minimize the sensation of the hypnic jerk by changing daytime activities. Sleep is easily improved through changes like eliminating caffeine, coping with anxiety, and exercising during the day. In some people, hypnic jerks are a more serious problem associated with other sleep disorders, which should be discussed with your doctor.

The mysteries of sleep have baffled mankind for centuries, but one thing is certain: There is nothing quite as satisfying as a good night’s sleep.