Hypnic jerk

Hypnic jerk
Hypnic jerk
Other names	Myoclonic jerk, hypnagogic jerk, sleep start, sleep twitch, night start
Specialty	Sleep medicine
Causes	Random involuntary muscle contraction of unknown causation without pathology plus possibly associated with fatigue, sleep deprivation, caffeine, anxiety

A hypnic jerk, hypnagogic jerk, sleep start, sleep twitch, myoclonic jerk, or night start is a brief and sudden involuntary contraction of the muscles of the body which occurs when a person is beginning to fall asleep, often causing the person to jump and awaken suddenly for a moment. Hypnic jerks are one form of involuntary muscle twitches called myoclonus.

Physically, hypnic jerks resemble the "jump" experienced by a person when startled, sometimes accompanied by a falling sensation.^[1] Hypnic jerks are associated with a rapid heartbeat, quickened breathing, sweat, and sometimes "a peculiar sensory feeling of 'shock' or 'falling into the void'".^[2] It can also be accompanied by a vivid dream experience or hallucination.^[3] A higher occurrence is reported in people with irregular sleep schedules.^[4] When they are particularly frequent and severe, hypnic jerks have been reported as a cause of sleep-onset insomnia.^[3]

Hypnic jerks are common physiological phenomena.^[5] Around 70% of people experience them at least once in their lives with 10% experiencing them daily.^[6]^[7] They are benign and do not cause any neurological sequelae.^[7]

^ "Brain Basics: Understanding Sleep" (PDF). National Institute of Neurological Disorders and Stroke. National Institutes of Health. 2006. Archived from the original (PDF) on 2019-07-03. Retrieved 2019-07-03. Many also experience sudden muscle contractions called hypnic myoclonia, often preceded by a sensation of starting to fall. These sudden movements are similar to the "jump" we make when startled.
^ Friedman, Lauren F. (2014-05-21). "Why You Sometimes Feel Like You're Falling And Jerk Awake When Trying To Fall Asleep". Business Insider. Retrieved 2016-07-17.
^ ^a ^b Oswald, Ian (1959-03-01). "Sudden Bodily Jerks on Falling Asleep". Brain. 82 (1): 92–103. doi:10.1093/brain/82.1.92. ISSN 0006-8950. PMID 13651496.
^ "Basics of Sleep Behavior: NREM and REM Sleep". Sleep Syllabus. Archived from the original on 2011-07-18. Retrieved 2019-07-03. These muscular contractions, called sleep related myoclonias are not pathological events, although they tend to occur more frequently with stress or unusual or irregular sleep schedules.
^ Sander, Howard; Geisse, Hildegarde; Quinto, Christine; Sachdeo, Rajesh; Chokroverty, Sudhansu (1998). "Sensory sleep starts". Journal of Neurology, Neurosurgery & Psychiatry. 64 (5): 690. doi:10.1136/jnnp.64.5.690. PMC 2170079. PMID 9598699.
^ Chokroverty, Sudhansu; Bhat, Sushanth; Gupta, Divya (2013). "Intensified Hypnic Jerks: A Polysomnographic and Polymyographic Analysis". Journal of Clinical Neurophysiology. 30 (4): 403–410. doi:10.1097/WNP.0b013e31829dde98. PMID 23912581. S2CID 38840788.
^ ^a ^b Vetrugno, Roberto; Montagna, Pasquale (2011). "Sleep-to-wake transition movement disorders". Sleep Medicine. 12: S11–S16. doi:10.1016/j.sleep.2011.10.005. PMID 22136891.

[bbasics-1] "Brain Basics: Understanding Sleep" (PDF). National Institute of Neurological Disorders and Stroke. National Institutes of Health. 2006. Archived from the original (PDF) on 2019-07-03. Retrieved 2019-07-03. Many also experience sudden muscle contractions called hypnic myoclonia, often preceded by a sensation of starting to fall. These sudden movements are similar to the "jump" we make when startled.

[Friedman2014-2] Friedman, Lauren F. (2014-05-21). "Why You Sometimes Feel Like You're Falling And Jerk Awake When Trying To Fall Asleep". Business Insider. Retrieved 2016-07-17.

[Oswald-3] Oswald, Ian (1959-03-01). "Sudden Bodily Jerks on Falling Asleep". Brain. 82 (1): 92–103. doi:10.1093/brain/82.1.92. ISSN 0006-8950. PMID 13651496.

[SSyllabus-4] "Basics of Sleep Behavior: NREM and REM Sleep". Sleep Syllabus. Archived from the original on 2011-07-18. Retrieved 2019-07-03. These muscular contractions, called sleep related myoclonias are not pathological events, although they tend to occur more frequently with stress or unusual or irregular sleep schedules.

[Sander-5] Sander, Howard; Geisse, Hildegarde; Quinto, Christine; Sachdeo, Rajesh; Chokroverty, Sudhansu (1998). "Sensory sleep starts". Journal of Neurology, Neurosurgery & Psychiatry. 64 (5): 690. doi:10.1136/jnnp.64.5.690. PMC 2170079. PMID 9598699.

[Chokroverty-6] Chokroverty, Sudhansu; Bhat, Sushanth; Gupta, Divya (2013). "Intensified Hypnic Jerks: A Polysomnographic and Polymyographic Analysis". Journal of Clinical Neurophysiology. 30 (4): 403–410. doi:10.1097/WNP.0b013e31829dde98. PMID 23912581. S2CID 38840788.

[Vetrugno-7] Vetrugno, Roberto; Montagna, Pasquale (2011). "Sleep-to-wake transition movement disorders". Sleep Medicine. 12: S11–S16. doi:10.1016/j.sleep.2011.10.005. PMID 22136891.

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