What can cause the body to “jerk” during sleep?
Sudden body jerks while falling asleep or when coming out of sleep are a normal part of the sleep process and nothing to worry about. The phenomenon is called the “hypnagogic jerk” as it occurs during “hypnagogia,”–Greek for “leading into sleep.”
The jerk is a sudden muscular contraction or a twitch. Some people experience it with the sensation of moving or falling, and may even have a brief dream in which they fall down simultaneously with the jerk, often awakening themselves. While everyone may have a hypnagogic jerk now and again, it’s more likely to be remembered by those who have erratic sleeping patterns.
It’s been hypothesized by some evolutionary psychologists that the hypnagogic jerk is a vestige of our primate heritage, back when we lived in trees as proto-humans. As the jerk occurs while the body relaxes into sleep, it could be an inherited trait to make sure that the sleeper is in a safe place, and won’t fall out of the branch once completely relaxed.
Just to cover the bases, it’s possible that some body jerks are related to Periodic Limb Movement. This symptom occurs with a wide variety of intensity, from small twitches and “shudders,” to painful involuntary thrashings of the limbs that leads to awakening. Mild cases that do not lead to awakening may not need to be treated – but if it’s affecting your partner’s sleeping, you may want to look into sharing a bigger bed so as not to disturb them every night.
If the symptoms worsen, and lead to your own awakenings and fractured sleep, you may want to get a professional opinion. Severe PLMs are also associated with Restless Leg Syndrome and other sleep disorders, and they can affect your overall health if not treated.
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