{{Short description|Involuntary twitching while falling asleep}} {{Infobox medical condition (new) | name = Hypnic jerk | synonyms = Hypnagogic jerk, sleep start, sleep twitch, night start | image = | caption = | pronounce = | field = Sleep medicine | symptoms = | complications = | onset = | duration = | types = | causes = Unknown | risks = Irregular sleep schedule, anxiety, excessive stimulant consumption, stress, smoking, antidepressants | diagnosis = Based on symptoms | differential = | prevention = | treatment = Medication, reducing stimulant consumption | medication = Clonazepam | prognosis = | frequency = }}
A '''hypnic jerk''' is defined as 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.<ref name="bbasics">{{Cite web |date=2006 |title=Brain Basics: Understanding Sleep |url=https://education.ninds.nih.gov/brochures/Brain-Basics-Sleep-6-10-08-pdf-508.pdf |archive-url=https://web.archive.org/web/20190703160419/https://education.ninds.nih.gov/brochures/Brain-Basics-Sleep-6-10-08-pdf-508.pdf |archive-date=2019-07-03 |access-date=2019-07-03 |website=National Institute of Neurological Disorders and Stroke |publisher=National Institutes of Health |quote="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."}}</ref> Hypnic jerks are associated with a rapid heartbeat, quickened breathing, sweat, and sometimes "a peculiar sensory feeling of 'shock' or 'falling into the void{{'"}}.<ref name="Friedman2014">{{Cite web |author=Friedman |first=Lauren F. |date=2014-05-21 |title=Why You Sometimes Feel Like You're Falling And Jerk Awake When Trying To Fall Asleep |url=http://www.businessinsider.com/what-is-a-hypnic-jerk-2014-5 |access-date=2016-07-17 |website=Business Insider|archive-url=https://web.archive.org/web/20250305111924/http://www.businessinsider.com/what-is-a-hypnic-jerk-2014-5|archive-date=5 March 2025}}</ref> They can also be accompanied by vivid dream experiences or hallucinations.<ref name="Oswald">{{cite journal |last1=Oswald |first1=Ian |author-link=Ian Oswald |date=1959-03-01 |title=Sudden Bodily Jerks on Falling Asleep |journal=Brain |volume=82 |issue=1 |pages=92–103 |doi=10.1093/brain/82.1.92 |issn=0006-8950 |pmid=13651496}}</ref> A higher occurrence is reported in people with irregular sleep schedules.<ref name="SSyllabus">{{cite web |title=Basics of Sleep Behavior: NREM and REM Sleep |url=http://www.sleephomepages.org/sleepsyllabus/fr-d.html |archive-url=https://web.archive.org/web/20110718165045/http://www.sleephomepages.org/sleepsyllabus/fr-d.html |archive-date=2011-07-18 |access-date=2019-07-03 |work=Sleep Syllabus |quote="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."}}</ref> When they are particularly frequent and severe, hypnic jerks have been reported as a cause of sleep-onset insomnia.<ref name="Oswald" />
Hypnic jerks are common physiological phenomena.<ref name="Sander">{{cite journal |last1=Sander |first1=Howard |last2=Geisse |first2=Hildegarde |last3=Quinto |first3=Christine |last4=Sachdeo |first4=Rajesh |last5=Chokroverty |first5=Sudhansu |title=Sensory sleep starts |journal=Journal of Neurology, Neurosurgery & Psychiatry |date=1998 |volume=64 |issue=5 |page=690 |doi=10.1136/jnnp.64.5.690|pmid=9598699 |pmc=2170079 }}</ref> Around 70% of people experience them at least once in their lives, with 10% experiencing them daily.<ref name="Chokroverty">{{cite journal |last1=Chokroverty |first1=Sudhansu |last2=Bhat |first2=Sushanth |last3=Gupta |first3=Divya |title=Intensified Hypnic Jerks: A Polysomnographic and Polymyographic Analysis |journal=Journal of Clinical Neurophysiology |date=2013 |volume=30 |issue=4 |pages=403–410 |doi=10.1097/WNP.0b013e31829dde98|pmid=23912581 |s2cid=38840788 }}</ref><ref name="Vetrugno">{{cite journal |last1=Vetrugno |first1=Roberto |last2=Montagna |first2=Pasquale |title=Sleep-to-wake transition movement disorders |journal=Sleep Medicine |date=2011 |volume=12 |pages=S11–S16 |doi=10.1016/j.sleep.2011.10.005|pmid=22136891 }}</ref> They are mostly benign and do not cause any neurological sequelae, though in severe cases, there can be pronounced negative effects on sleep time and quality.<ref name="Vetrugno" /><ref>{{Cite journal |last1=Mah |first1=Cheri |last2=West |first2=Leslie |last3=Hekmat |first3=Anahid |date=2022-05-25 |title=0807 Sleep-related hiccups: A case report of antidepressant associated hypnic jerks |url=https://academic.oup.com/sleep/article/45/Supplement_1/A350/6592756 |journal=Sleep |language=en |volume=45 |issue=Supplement_1 |pages=A350 |doi=10.1093/sleep/zsac079.803 |issn=0161-8105}}</ref>
== Causes ==
=== Risk factors === According to the American Academy of Sleep Medicine (AASM), there is a wide range of potential causes, including anxiety, stimulants like caffeine and nicotine, stress, and strenuous activities in the evening. It may also be facilitated by fatigue or sleep deprivation.<ref name="Vetrugno" /> Additionally, antidepressant usage has been noted as a potential risk factor for hypnic jerks.<ref name="Sathe" /> However, most hypnic jerks occur essentially at random in healthy people.<ref>{{Cite journal |last1=Whitney |first1=Robyn |last2=Weiss |first2=Shelly K. |date=2018-03-01 |title=Sleep-Related Movement Disorders: Hypnic Jerks |url=https://link.springer.com/article/10.1007/s40675-018-0104-9 |journal=Current Sleep Medicine Reports |language=en |volume=4 |issue=1 |pages=19–27 |doi=10.1007/s40675-018-0104-9 |issn=2198-6401 |quote=...clustering of hypnic jerks can occur in normal healthy individuals and does not necessarily indicate an underlying pathology.|url-access=subscription }}</ref> Nevertheless, these repeated, intensifying twitches can cause anxiety in some individuals and a disruption to their sleep onset.<ref name="Chokroverty" />
According to a study on sleep disturbances in the ''Journal of Neural Transmission'', a hypnic jerk occurs during the non-rapid eye movement sleep cycle and is an "abrupt muscle action flexing movement, generalized or partial and asymmetric, which may cause arousal, with an illusion of falling".<ref name="Askenasy">{{Cite journal| title= Sleep Disturbances in Parkinsonism| journal=Journal of Neural Transmission| year=2003 |pages=125–50| publisher=Springer-Verlag| last=Askenasy |first=J. J. M.| doi=10.1007/s007020300001| volume=110| issue=2| pmid=12589574| s2cid=9147326}}</ref> Hypnic jerks are more frequent in childhood with 4 to 7 per hour in the age range from 8 to 12 years old, and they decrease to 1 or 2 per hour by 65 to 80 years old.<ref name="Askenasy" />
=== Theories === The causes of hypnic jerk are unclear and are being studied. None of the several theories that have attempted to explain it has been fully accepted.<ref>{{cite web |title=Hypnic (Hypnagogic) Jerking Explained – The Comprehensive Guide For 2019 |url=https://www.sleepadvisor.org/hypnic-jerking/ |website=Sleep Advisor |access-date=27 June 2019|archive-url=https://web.archive.org/web/20250322021051/https://www.sleepadvisor.org/hypnic-jerking/|archive-date=22 March 2025}}</ref> One hypothesis posits that the hypnic jerk is a form of reflex, initiated in response to normal bodily events during the lead-up to the first stages of sleep, including a decrease in blood pressure and the relaxation of muscle tissue.<ref>{{cite web |last1=Castro |first1=Joseph |title=Why Do People 'Twitch' When Falling Asleep? |url=https://www.livescience.com/39225-why-people-twitch-falling-asleep.html |website=LiveScience|date=21 November 2017 |archive-url=https://web.archive.org/web/20250310081544/https://www.livescience.com/39225-why-people-twitch-falling-asleep.html|archive-date=10 March 2025}}</ref> Another theory postulates that the body mistakes the sense of relaxation that is felt when falling asleep as a sign that the body is physically falling. As a consequence, it causes a jerk motion to wake the sleeper up so they can catch themselves.<ref name="Complete Guide to Hypnic Jerks">{{cite web |title=Complete Guide to Hypnic Jerks |url=https://hacktosleep.com/complete-guide-to-hypnic-jerks/ |website=Hack to Sleep: a guide to better sleep |date=26 March 2019 |access-date=1 July 2019}}</ref> A researcher at the University of Colorado suggested that a hypnic jerk could be "an archaic reflex to the brain's misinterpretation of muscle relaxation with the onset of sleep as a signal that a sleeping primate is falling out of a tree. The reflex may also have had selective value by having the sleeper readjust or review his or her sleeping position in a nest or on a branch in order to assure that a fall did not occur", but evidence is lacking.<ref name=Friedman2014 />
== Diagnosis == Hypnic jerks are often mistaken for other forms of movement during sleep, including:
* Restless legs syndrome * Periodic limb movement disorder * Hypnagogic foot tremor * Rhythmic movement disorder * Hereditary or essential startle syndrome
Some phenomena can help to distinguish hypnic jerk from these other conditions. For example, the occurrence of hypnic jerk arises only at sleep onset and it happens without any rhythmicity or periodicity of the movements and EMG bursts. Other pertinent history can also be used to differentiate it.<ref name="Chokroverty" />
This physiological phenomenon can also be mistaken for myoclonic seizure, but it can also be distinguished by different criteria, such as the fact that hypnic jerk occurs at sleep onset only or that the EEG is normal and constant. In addition, unlike seizures, there are no tongue bites, urinary incontinence, or postictal confusion in hypnic jerk. This phenomenon can therefore be distinguished from other, more serious conditions.<ref name="Chokroverty" />
During an epilepsy and intensive care study, the lack of a preceding spike discharge measured on an epilepsy monitoring unit, along with the presence only at sleep onset, helped differentiate hypnic jerks from epileptic myoclonus.<ref name="Fisch2009">{{cite book|author=Bruce J Fisch, MD|title=Epilepsy and Intensive Care Monitoring: Principles and Practice|url=https://books.google.com/books?id=kIISvcXYQ94C|date=23 October 2009|publisher=Demos Medical Publishing|isbn=978-1-935281-59-7}}</ref>
== Treatment == There are ways to reduce hypnic jerks, including reducing consumption of stimulants such as nicotine or caffeine, avoiding physical exertion prior to sleep.<ref name="Sathe">{{cite journal |last1=Sathe |first1=Harshal |last2=Karia |first2=Sagar |last3=Desousa |first3=Avinash |last4=Shah |first4=Nilesh |title=Hypnic jerks possibly induced by escitalopram |journal=Journal of Neurosciences in Rural Practice |date=2015 |volume=6 |issue=3 |pages=423–424 |doi=10.4103/0976-3147.158797|pmid=26167034 |pmc=4481805 |doi-access=free }}</ref>
Some medications can also help to reduce or eliminate the hypnic jerks. For example, low-dose clonazepam at bedtime may make the twitches disappear over time.<ref name="Chokroverty" /> While antidepressant usage is a potential risk factor for hypnic jerks, a combination of clonazepam and antidepressants has been found to potentially mitigate hypnic jerks in those with depression and hypnic jerks.<ref>{{Cite journal |last1=Kumar |first1=Rakesh |last2=Ali |first2=Syed Naiyer |last3=Saha |first3=Shatabdi |last4=Bhattacharjee |first4=Subir |date=July 2023 |title=SSRI induced hypnic jerks: A case series |journal=Indian Journal of Psychiatry |language=en |volume=65 |issue=7 |pages=785–788 |doi=10.4103/indianjpsychiatry.indianjpsychiatry_207_23 |doi-access=free|issn=0019-5545 |pmc=10461585 |pmid=37645359}}</ref>
In addition, some people may develop a fixation on these hypnic jerks, leading to increased anxiety about the disruptive experience. This increased anxiety and fatigue increase the likelihood of experiencing these jerks, resulting in a positive feedback loop.<ref name="Hypnic Jerks: How To Avoid Waking With A Jolt">{{cite web |last1=Green |first1=Ethan |title=Hypnic Jerks: How To Avoid Waking With A Jolt |url=https://www.nosleeplessnights.com/the-hypnic-jerk-jolted-awake-when-falling-asleep/ |website=No Sleepless Nights |date=April 16, 2013 |access-date=3 July 2019 |archive-date=1 July 2019 |archive-url=https://web.archive.org/web/20190701053742/https://www.nosleeplessnights.com/the-hypnic-jerk-jolted-awake-when-falling-asleep/ }}</ref>
== See also == * {{annotated link|Exploding head syndrome}} * {{annotated link|Fasciculation}} * {{annotated link|Hypnagogia}} * {{annotated link|Myoclonus}} * {{annotated link|Periodic limb movement disorder}} * {{annotated link|Rapid eye movement sleep}} * {{annotated link|Sleep paralysis}}
== References == {{Reflist}}
{{Medical resources | ICD10 =<!-- {{ICD10| }} --> | ICD9 =<!-- {{ICD9|xxx}} --> | ICDO = | OMIM = | DiseasesDB = | MedlinePlus = | eMedicineSubj = | eMedicineTopic = | MeshID = }} {{SleepSeries2}}
{{DEFAULTSORT:Hypnic Jerk}} Category:Sleep disorders