What is a Hypnic Jerk?
A hypnicÂ jerk is an involuntary twitch of muscles, which occurs as theÂ person just begins to fall asleep.Â It is often described as the sudden sharp movement, which is similar to the movement made when someone is startled. Irregular sleeping schedules and trying to fall asleep after being sleep deprived may be the factors behind hypnic jerks.
What Causes Hypnic Jerks?
The exact reasons behind hypnic jerks is not known. However, there are two theories which explain why these occur.
According to the first theory, as we drift into sleep, our body undergoes a transition. The heart rate and breathing rate slows down. The muscle tone also changes. This muscular transition while sleeping is suggested to be the reason behind hypnic jerks.
The second theory says that, while falling asleep, our muscles relax. This relaxation is sometimes intepreted by brain as a sign falling. So, in an attempt to keep you upright, you would thrash your legs and have a jerk.
Hypnic jerks usually occur once or twice per night. When you are deprived of sleep and are trying to sleep, you can expect more of these jerks. Some less intense jerks may occur several times during sleep, but they may not wake you up and you may not realize them.
In some cases, people have a series of jerks at regular time intervals. This is known as periodic limb movement disorder (PLMB) and it can indicate a sleep disorder. You should consult your doctor if you have these symptoms.
If you have a hypnic jerk, once in a while, there is no need to be concerned. But, if its affecting your sleep and disturbing your sleeping partner, do consult your doctor.