Startle During Sleep

If you ever experienced a jolt or a falling feeling as you drift to sleep, don’t worry; they are not dangerous and are part of the normal sleep physiology. These body jerk sensations are given the medical terms “hypnic jerk” or “sleep starts”. Sometimes a person might experience a visual hallucination with them, a brief flash of dream.

They tend to occur in individuals who have irregular sleep and wake schedules- in other words, in folks who are sleep deprived. Anxiety and stress make them worse.

No one is sure why they happen, but sleep scientists believe that when you sleep, most of your brain is in a sleep state, but there might be a part that is awake. It might happen because as you fall asleep and your muscles become very relaxed, your brain thinks “ops you are falling” and “let me save you” so by getting your muscle tone back to work, that when the jolt happens.

Hypnic jerks must be distinguished other types of sleep-related events that require medical attention. Brief and frequent arousals that occur due to snoring or apneas (cessation of breathing during sleep) might be a sign of obstructive sleep apnea syndrome. Frequent body or leg jerks are seen with restless legs or periodic limb movements of sleep. Body jerks can also be a sign of seizure or epilepsy especially if they occur in clusters or groups. If these jerks occur frequently at night, consult with your doctor to make sure that the events are truly hypnic jerks and not a sign of sleep apnea or seizures.

Otherwise, simple hypnic jerks are benign. If they become frequent, they can certainly cause disruption of the sleep quality. So paying attention to adequate and good quality sleep is important.



  • Improve your sleep quality. Ensure adequate sleep. Avoid variations in sleep-wake schedule. Avoid caffeine and alcohol. Address stress and anxiety. None of these are easy but they are worth the effort.
  • Sleeping pills are not indicated for hypnic jerks.
  • If you suspect that they are not simple hypnic jerks, consult your physician to make sure that they are not part of the sleep apnea or seizures or periodic leg jerks.