Home » Sleep Disorders » Sleep Starts
January 2021 |  Reviewed by:  Shelley Hershner, MD and Reeba Mathew, MD

What are sleep starts?

Do you have sudden, brief jerks of your body as you fall asleep? Do these jerks mainly affect your arms and legs? Do they occur along with one or more of the following sensations?

  • A feeling that you are falling
  • A sensory flash
  • A visual dream or hallucination

If you answered yes to these questions, then you may have sleep starts.

Sleep starts are also known as hypnic or hypnagogic jerks. They are sudden, brief, and strong contractions of the body or one or more body segments. They occur as you are falling asleep. Some people also have a sensation of falling.

Sleep starts usually consist of one strong jerk that affects much of the body. The arms and legs are most likely to be affected. A sharp cry may also occur. A sleep start does not always wake you up. This means that you may not recall a jerk that was noted by a bed partner.

At times, many jerks may occur one after another. They can be frequent, intense, and repetitive. Intense or frequent sleep starts may lead to a fear of falling asleep. This can also lead to anxiety and worry. Sleep loss may result if repeated jerks keep you awake. Anxiety caused by sleep starts can also make it hard to fall asleep. Insomnia can result if this problem continues over time.

It is possible to be injured by a sleep start. The jerk may cause you to bruise a foot against the bed or kick a bed partner.

What are risk factors of sleep starts?

Sleep starts are very common. They are a fairly universal part of the process of falling asleep. They may not seem so common because they often are not recalled.

They have been reported to occur in 60% to 70% of people. In most people, they only occur from time to time. Sleep starts affect all ages and both men and women. Adults are more likely to complain about frequent or intense jerks.

The frequency and intensity of sleep starts can be increased by the following:

  • A high intake of caffeine or other stimulants
  • Prior intense physical work or exercise
  • Sleep deprivation
  • Emotional stress

It is also important to know if there is something else that is causing your sleep problems. Instead of being sleep starts, your problems might result from the following:

  • Another sleep disorder
  • A medical condition
  • Medication use
  • A mental health disorder
  • Substance abuse