Why do we startle when we fall asleep?

Do you really know?

You're peacefully drifting off to sleep when suddenly you feel as if you're falling into a void and you startle awake. This rather unpleasant sensation is known as a ‘hypnic jerk’ and is a common occurrence. It is an involuntary muscle spasm, a bit like a hiccup, also known as ‘myoclonus’. Sometimes, this sensation is accompanied by the feeling or the dream that you are falling.

These twitches are your body’s bedtime quirks, popping up in the twilight zone of sleep – that light stage between being awake and snoozing soundly in deep sleep. They’re like an accidental alarm that can, annoyingly, snap us back to reality. As we drift off, our muscles take a breather, but our brain does a quick systems check to ensure everything’s alright, triggering that startling reflex.

What’s happening when we experience these sudden spasms? Can anything amplify this startling sensation? Should we be worried about these nighttime jolts? In under 3 minutes, we answer your questions!

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A podcast written and realised by Amber Minogue.

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