Have you ever woken up with a jerk as if been thrown into your bed? Or fallen from a virtually enormous height onto your bed? These are known as “hypnic jerks” or “sleep start” and as many as 70% of people experience them from time to time. This parasomnia occurs only during the hypnagogic state, the transitional period between wakefulness and sleep.
SO WHY DOES THIS HAPPEN?
This phenomenon is extremely common, but surprisingly, scientists are only just now beginning to understand what causes this. You may think that perhaps something loud happened in the room and that it woke you up, but this is not necessarily the case.
Scientists noticed that “hypnic jerk” occurs most commonly when you fall asleep very quickly from major exhaustion. In the initial stages of sleep, your heart rate and breathing slow down quickly. But sometimes when you are extremely exhausted, the brain proceeds through this stage of sleep too quickly, confusing itself into thinking that the body and its major systems are failing and you are dying.
The body quickly responds by jolting you awake with a burst of chemicals, one that the brain might interpret, and then build a dream designed to wake you up, which is the basic premise behind the theory of the ‘hypnic jerk.’
Some scientists also believe certain factors, such as stress, anxiety, fatigue, caffeine and sleep deprivation, may increase the frequency or severity of hypnagogic jerks. Luckily, there’s nothing to be worried about hypnic jerks because they are nothing serious. If one wakes you up, simply roll over and go back to sleep.
Source: Interesting Facts & Information