WHAT CAUSES…JERKING AWAKE IN BED?

You are in bed, all comfy and sleepy when – bam! – you are suddenly jolted awake. These disconcerting episodes are called hypnic jerks or sleep starts. They are sudden, involuntary muscle contractions that occur when falling asleep. Hypnic is short for hypnagogic, a word describing the transition between wakefulness and sleep. They usually only affect one side of the body, such as your left arm and left leg. The cause is uncertain, but according to the Sleep Foundation, hypnic jerks start in the same part of your brain that controls your startle response. The Foundation says, “It may be that when your muscles relax completely, even though this is a normal part of falling asleep, your brain mistakenly assumes you are really falling and reacts by twitching your muscles. It may also be possible that hypnic jerks are a physical reaction to the dream-like imagery that accompanies them.”

They are harmless but more likely if you’ve had too much coffee or alcohol, been exercising before sleep or are stressed or over-tired.