DADADEL
Have you ever fallen asleep, dreamt you were falling, and suddenly jerked awake? It’s a strange, often unsettling experience known as a hypnic jerk, and if it’s happened to you, you’re far from alone. A 2016 study found that 60-70% of people experience these involuntary movements.
Before we dive into the cause of hypnic jerks, let’s review the stages of sleep:
Stage One
Stage one occurs as you begin to nod off. This brief period, lasting just a few minutes, is when your heartbeat, breathing, and eye movements slow down, and your muscles relax. You may experience occasional twitches as your brain waves shift from wakefulness to sleep.
Stage Two
In this stage of light sleep, your body prepares for deeper rest. Your heartbeat and breathing slow even further, muscles relax, and body temperature drops. Eye movements cease, and while brain activity decreases, brief bursts of electrical activity still occur.
Stage Three
This is the stage that makes you feel refreshed when you wake up. Your heartbeat and breathing slow to their lowest points, muscles remain relaxed, and waking up becomes more difficult.
REM Sleep
About 90 minutes after you fall asleep, you enter REM sleep. Your eyes move rapidly, and brain activity becomes similar to that of being awake. Breathing becomes irregular, and heart rate and blood pressure increase. This is when most dreaming occurs, and you cycle through all stages four to five times each night, with the duration of each stage varying.
Hypnic Jerks
Hypnic jerks, also called hypnagogic jerks or sleep starts, are involuntary movements that occur as you transition from wakefulness to sleep. Although the exact cause remains unclear, they are more common when you’re sleep-deprived and trying to stay engaged in an activity. Rafael Pelayo, a sleep specialist at Stanford Sleep Medicine Center, explains that they happen because some parts of your nervous system are awake while others are falling asleep.
These jerks can be thought of as misfires from your nervous system, sending mixed signals as your body shifts from wakefulness to stage one sleep. Normally, REM sleep occurs after 90 minutes, but if you’re severely sleep-deprived, your body may skip stages two and three, jumping straight to REM. According to Pelayo, a hypnic jerk is your body’s way of signaling that it desperately needs sleep, and “nothing else is going to satisfy that urge.”
While hypnic jerks can feel alarming, they are harmless and don’t require treatment. Some people may feel anxious afterward and struggle to fall back asleep. If this happens to you, reminding yourself that it’s a normal phenomenon can help you relax and drift back to sleep.
Occasionally, hypnic jerks can occur in situations where sleep isn’t an option, such as during a lecture or meeting. If this happens frequently, Pelayo suggests a few strategies to stay alert:
- Focus on something more engaging than falling asleep.
- Make eye contact with the speaker.
- Drink coffee beforehand if you anticipate feeling drowsy.
To avoid these jolts altogether, make sure you get seven to nine hours of sleep each night. Though harmless, hypnic jerks are often a sign that you’re not getting enough rest. If they happen regularly, reflect on your sleep habits and consider making adjustments.
