Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors
Search in posts
Search in pages
Filter by Categories
Book Review
Brief Report
Case Letter
Case Report
Case Series
Commentary
Current Issue
Editorial
Erratum
Guest Editorial
Images
Images in Neurology
Images in Neuroscience
Images in Neurosciences
Letter to Editor
Letter to the Editor
Letters to Editor
Letters to the Editor
Media and News
None
Notice of Retraction
Obituary
Original Article
Point of View
Position Paper
Review Article
Short Communication
Systematic Review
Systematic Review Article
Technical Note
Techniques in Neurosurgery
Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors
Search in posts
Search in pages
Filter by Categories
Book Review
Brief Report
Case Letter
Case Report
Case Series
Commentary
Current Issue
Editorial
Erratum
Guest Editorial
Images
Images in Neurology
Images in Neuroscience
Images in Neurosciences
Letter to Editor
Letter to the Editor
Letters to Editor
Letters to the Editor
Media and News
None
Notice of Retraction
Obituary
Original Article
Point of View
Position Paper
Review Article
Short Communication
Systematic Review
Systematic Review Article
Technical Note
Techniques in Neurosurgery
Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors
Search in posts
Search in pages
Filter by Categories
Book Review
Brief Report
Case Letter
Case Report
Case Series
Commentary
Current Issue
Editorial
Erratum
Guest Editorial
Images
Images in Neurology
Images in Neuroscience
Images in Neurosciences
Letter to Editor
Letter to the Editor
Letters to Editor
Letters to the Editor
Media and News
None
Notice of Retraction
Obituary
Original Article
Point of View
Position Paper
Review Article
Short Communication
Systematic Review
Systematic Review Article
Technical Note
Techniques in Neurosurgery
View/Download PDF

Translate this page into:

Original Article
14 (
2
); 272-275
doi:
10.25259/JNRP_16_2022

The prevalence of sleep paralysis in medical students in Buenos Aires, Argentina

Department of Mental Health, División Neuropsicofarmacología, Hospital de Clínicas “José de San Martín,”, Buenos Aires, Argentina, United States
Department of Psychiatry, Adena Medical Center, Ohio, United States
Corresponding author: Juan Manuel Duarte, División Neuropsicofarmacología, Hospital de Clínicas “José de San Martín,” Buenos Aires, Argentina. jduarte@fmned.uba.ar
Licence
This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

How to cite this article: Duarte JM, Lisi GR, Carroll BT, Garro MF, Appiani FJ. The prevalence of sleep paralysis in medical students in Buenos Aires, Argentina. J Neurosci Rural Pract 2023;14:272-5.

Abstract

Objectives:

The objectives of this study were to determine the prevalence of sleep paralysis (SP) in medical students from the University of Buenos Aires (UBA).

Materials and Methods:

An ad hoc questionnaire based on the diagnosis of SP and a demographic survey was electronically presented to students of Internal Medicine at the School of Medicine of the UBA. The respondents answered both questionnaires using Google Forms®.

Results:

The prevalence of SP was 40.7% (95% CI 33.5–47.8). A higher percentage of the respondents (76%) reported experiencing SP-related anxiety. An association between self-perceived quality of sleep and the incidence of SP was found (χ2: 12.712, P = 0.002). The highest frequency was hypnopompic SP (55.55%), and the highest percentage (55.4%) suffered from SP less than once every 6 months. Most respondents (59.5%) reported having started with SP symptoms after 18 years of age, and the highest percentage (66.2%) had exacerbated their symptoms at college. The frequency of the Incubus phenomenon was 14.5% (95% CI 6.2–23). Most respondents (70.8%) denied the association of SP with religious or paranormal beliefs.

Conclusion:

SP is highly prevalent in medical students and is associated with poor sleep habits and perceived poor sleep quality. Clinicians should be aware of this parasomnia to avoid a misdiagnosis of psychosis and inform sufferers of the nature of SP.

Keywords

Sleep paralysis
Parasomnia
Rapid eye movement sleep
Medical students

INTRODUCTION

Sleep paralysis (SP) is an unpleasant disorder that occurs when falling asleep (hypnagogic) or waking up (hypnopompic). The American Association of Sleep Medicine defines it as the impossibility of moving the trunk or extremities at the beginning of the dream or when waking up, from a few seconds to minutes of duration, that cause significant distress and cannot be explained by other medical or psychiatric causes[1] [Table 1]. The primary SP corresponds to the isolated SP, which can be recurrent. However, it can be part of the symptom complex in patients with narcolepsy.[2]

Table 1: Diagnostic criteria of sleep paralysis according to the International Classification of Sleep Disorders, 3rd edition.[1]
Inability to move the trunk or the limbs at sleep onset or upon awakening
Each episode lasts from a few seconds to a few minutes
Each episode causes significant distress: bedtime anxiety or fear of sleep
Not explained by another sleep disorder (narcolepsy), mental disorder, medical condition, medication or substance use

This disorder is related to rapid eye movement (REM) sleep due to the dissociation between this period of sleep and awakening.[3] Its prevalence in the general population is 7.6%, with higher percentages in university students, patients with panic disorders, and other psychiatric illnesses. This disorder most frequently begins between the ages of 13 and 18, although it can be found at an earlier or later age.[4] Sometimes, patients with SP do not consult a doctor for fear of public opinion.[5] Furthermore, it is common for general practitioners to be unaware of the entity, which leads to erroneous diagnoses such as psychosis.[6]

The result of an assessment carried out in 2016, where 58% of a sample of medical students from the University of Buenos Aires (UBA) had poor sleep quality.[7] paved the way to the objective of this work, that determines the prevalence of SP in a sample of medical students from the UBA.

MATERIALS AND METHODS

An ad hoc questionnaire based on the diagnostic criteria of SP was electronically sent, along with a questionnaire considering demographic data (age, gender, and self-perception of sleep quality). Questions were asked about symptoms, sleep habits, the presence and type of hallucinations during the episodes (including the incubus phenomenon), triggers, and associated cultural beliefs. This questionnaire was sent to students of Internal Medicine of the School of Medicine of the UBA, who answered it through the Google Forms® platform after signing an informed consent form.

This study was carried out under the ethical standards that govern research on human beings, under Law 25326 of the Argentine Republic and the Helsinki Declaration in its latest version (Fortaleza, 2013). The ethics committee of the Hospital de Clínicas “José de San Martín” approved this research project.

The statistical analysis was bivariate, using percentages and their 95% confidence intervals (95% CI) to determine prevalence and frequency; χ2 tests or Fisher’s exact test were used to search for the association of nominal variables. Age was compared using the parametric ANOVA test. SPSS® version 24 was used for statistical analysis.

RESULTS

The survey was sent to 190 students, but 182 participants (95.80%) responded: 42 males, 138 females, and two who defined themselves as “another gender.” The mean age of the participants was 25.39 ± 4.379 years, with no significant differences between the female, male, and other genders.

The prevalence of SP in the analyzed sample was 40.7% (n = 74), with no significant differences in gender. Results showed that a high percentage of participants reported suffering from SP-related anxiety (76.5%, n = 56).

Another relevant finding was the association found between self-perceived quality of sleep quality (good vs. fair or poor sleep quality) and the incidence of SP (χ2: 12.712, P = 0.002).

The highest prevalence of SP was hypnopompic (55%, n = 40). The highest frequency of symptoms was less than once every 6 months, or only once in life (55.4%, n = 41), followed by two or more times in 6 months. Only one respondent (1.4%) reported having symptoms more than once per night.

The highest percentage of participants reported having started SP symptoms after the age of 18 (59.5%, n = 44); the lowest percentage reported having had PS symptoms before the age of 13 (9.5%, n = 7).

A total of 97.3% (n = 72) reported not having seen a doctor for these episodes, and 66.2% (n = 49) informed that symptoms were exacerbated when they were at university. About 55% (n = 41) did not report a family history of sleep disorders.

Most respondents (62.2%, n = 46) reported having bad self-perceived sleep habits, while total of 54.1% (n = 40) did not report the presence of SP triggers.

Regarding hallucinations, 50% (n = 37) reported auditory hallucinations during episodes of PS, followed by visual hallucinations (47.3%, n = 35), whereas 10.8% (n = 8) reported no symptoms accompanying PS. The highest percentage (25%) reported having only one accompanying symptom; 2.8% (n = 2) reported having eight accompanying symptoms: visual and auditory hallucinations, feeling of a presence, shortness of breath, feeling of the mattress sinking, feeling observed, terror, and Incubus phenomenon. The frequency of the Incubus phenomenon in those with SP was 14.9% (n = 11) [Table 2].

Table 2: Frequency of associated symptoms in respondents with sleep paralysis.
Symptoms n % 95% CI
Visual hallucinations 37 50 39.2–62.2
Auditory hallucinations 35 47.3 41.9–63.5
Fear 35 47.3 41.9–63.5
Feeling of a presence 32 43.2 32.4–54.1
Feeling breathless 25 35.1 24.3–45.9
Feeling of a sagging mattress 19 25.7 16.2–35.1
Feeling of being observed 18 24.3 14.9–35.1
Incubus phenomenon 11 14.9 6.8–23
None of the above 8 10.8 4.1–17.6

Most respondents (70.8%, n = 52) denied the association of the symptoms with any religious or paranormal beliefs. Only 6.8% (n = 5) associated SP symptoms with a paranormal phenomenon, and 14.9% believed that they were going crazy due to the symptoms of SP.

Related to gender, there was no significant difference to be reported.

DISCUSSION

The prevalence of SP in the analyzed sample was 40.8%, which was higher than that reported in the general population. This percentage was lower than that found in a study of medical students from Lima (49.7%),[8] but higher than that reported in other published studies.[9-11] In addition, the prevalence found in this study was higher than that reported in other studies evaluating university students in general.[12-15]

In this study, poor sleep quality was associated with SP. This finding was consistent with what has been published in other studies.[7,8,15,16] In addition, the majority of those surveyed with PS reported poor sleep habits. Poor sleep quality is an independent predictor of SP and is mainly associated with prolonged sleep latency, daytime dysfunction due to poor sleep, and insomnia that occurs five or more times per month. In addition, it has been found that the variation of the PER2 gene (circadian rhythm regulator) influences the appearance of SP and poor sleep quality. Finally, going to sleep after midnight increases the odds of SP.[17]

About 89.2% reported having hallucinatory symptoms: the majority, in the form of visual hallucinations, followed by auditory hallucinations, terror, and the sensation of a presence. Smaller percentages reported feeling of sinking in the mattress and the feeling of being observed. These values were similar to those found in the San Marcos University study regarding visual and auditory hallucinations. However, the prevalence of hallucinations among medical students from Ecuador was much lower, predominately visual ones. [8] Hallucinatory phenomena are vivid, elaborate, multimodal and terrifying. These phenomena are related to the abnormal state of REM sleep caused by exogenous and endogenous inputs from oculomotor or middle ear activity. Signals from the brainstem to the thalamus project to the cerebral cortex, amygdala, and cingulate cortex.[18] Concomitantly, paralysis occurs due to GABAergic and glycinergic projections originating in the pontine reticular formation and ventromedial region of the medulla on the interneurons of the spinal cord. During SP, wakefulness occurs at the same time as muscle atony. There is desynchronization between motor performance and sensory input. Sensoperceptive phenomena occur due to the activation of the temporoparietal junction and the parietal lobe on the right side: these two structures are necessary for the neural representation of the human body. This activation is mediated by serotonin through its 5-HT2A receptors: thus, meaningless stimuli acquire meaning.[19] In SP, the appropriate medical term for these phenomena should be hallucinosis.

The Incubus phenomenon is a hallucinosis that consists of a creature sitting or lying on the thorax, which can carry out violent or sexual activity during the SP episode. Vegetative symptoms and, sometimes, sexual arousal occur during this phenomenon. In this case, the SP ends abruptly when that deluded creature falls. This phenomenon can lead to insomnia, comorbid anxiety, or comorbid delusional disorder but should not be confused with schizophrenia. The prevalence of this phenomenon in the general population is 19%,[20] slightly higher than that found in this study (14.9%). According to mythological beliefs, an Incubus is a demon that lies down on women engaging in sexual activity with them. This phenomenon was first described in the 17th century by Isbrand van Diemerbroeck.[21]

A few respondents related the episodes of SP with a paranormal belief. A study conducted at the University of Manchester found a weak association between paranormal beliefs and SP.[22]

SP is a form of parasomnia associated with REM sleep. Under physiological conditions, this stage of sleep is triggered by the cholinergic activity of the neurons of the lateral dorsal tegmental nuclei (REM-on neurons) and the inhibition of the serotonergic and noradrenergic activity of the pontine neurons and the floor of the IV ventricle (REM-off neurons). The REM-on neurons facilitate the activity of the reticularispontis-oralis region and, from there, ascending signals (such as the desynchronization of the electroencephalogram, eye movements and ponto-geniculo-occipital waves), and descending ones (causing muscle atony) are emitted.[23] According to the activation-input-modulation framework, there is significant activation, external and internal inputs, and mixed neuromodulation: cholinergic and serotonergic in SP. Polysomnographic recordings show mixed electroencephalographic activity (with alpha waves and REM activity), and an absence of electromyographic activity due to muscle atony.[17]

A systematic review with meta-analysis did not show a predilection for age, sex or ethnicity.[16] In this study, no differences were found in relation to any of the variables explored in terms of gender. The highest percentage reported having symptoms that started after the age of 18, and the majority reported that the attacks of SP were exacerbated by university studies. Finally, the highest percentage reported feeling anxiety during the episodes. Medical students have high academic demands and poor sleep quality.

The presence of an underlying psychiatric condition cannot be ruled out, and it cannot be determined whether episodes of PS are isolated or associated with narcolepsy. PS has been associated with dissociative experiences, panic attacks, post-traumatic stress disorder, history of childhood sexual abuse,[4,16] mood disorders, and bipolar disorder.[24] A passive-aggressive personality has been associated with the occurrence of SP;[25] however, some authors did not find a connection between personality traits and this parasomnia.[26]

CONCLUSION

SP is highly prevalent in medical students and is associated with poor sleep habits and poor self-perceived sleep quality. Most of the accompanying hallucinations were visual and auditory, and the prevalence of the Incubus phenomenon was lower than that previously reported. General practitioners need to consider this parasomnia through questioning and polysomnography to avoid misdiagnosis of a psychotic episode and to reduce the anguish of those who suffer from it. Informing them of the nature of the condition, its characteristics, control measures, and knowledge of its benign nature improves the quality of life of the person who suffers from SP.

Acknowledgments

The authors are thankful to Professor Sofia Fernandez MD, for authorizing the realization of this research work.

Declaration of patient consent

The authors certify that they have obtained all appropriate consent.

Conflicts of interest

There are no conflicts of interest.

Financial support and sponsorship

Nil.

References

  1. . Recurrent isolated sleep paralysis In: International Classification of Sleep Disorders (3rd ed). Darien IL: American Academy of Sleep Medicine; .
    [Google Scholar]
  2. . Narcolepsy and idiopathic hypersomnia In: Chokroverty S. editors. Sleep Disorders Medicine. New York: Springer; . p. :697-711.
    [CrossRef] [Google Scholar]
  3. . International classification of sleep disorders-third edition: Highlights and modifications In: Chest. Vol 146. . p. :1387-94.
    [CrossRef] [PubMed] [Google Scholar]
  4. , . Lifetime prevalence rates of sleep paralysis: A systematic review. Sleep Med Rev. 2011;15:311-5.
    [CrossRef] [PubMed] [Google Scholar]
  5. . Sleep paralysis: An overview. JINYA. 2020;3:19-24.
    [Google Scholar]
  6. . Comments on sleep paralysis. Transcult Psychiatry. 2006;43:692-4.
    [CrossRef] [PubMed] [Google Scholar]
  7. , , , , , , et al. Dream quality and sleep paralysis in medical students. An Fac Med Lima. 2006;67:339-44.
    [CrossRef] [Google Scholar]
  8. , . Parálisis y Alucinaciones del Sueño en Estudiantes de la Facultad de Medicina de la Pontificia Universidad Católica de Ecuador y su Asociación Con la Privación de Sueño en los Meses de Septiembre a Noviembre de 2015. Tesis de Grado. Available from: https://www.repositorio.puce.edu.ec/handle/22000/10416 [Last accessed on 2022 Sep 30]
    [Google Scholar]
  9. , , . Sleep paralysis among medical students. J Psychol. 1981;107:247-52.
    [CrossRef] [PubMed] [Google Scholar]
  10. , , , . The pattern of isolated sleep paralysis among Nigerian medical students. J Natl Med Assoc. 1989;81:805-8.
    [CrossRef] [PubMed] [Google Scholar]
  11. , , . Experiences of sleep paralysis in a sample of Irish university students. Ir J Med Sci. 2011;180:917-9.
    [CrossRef] [PubMed] [Google Scholar]
  12. , , , , , , et al. Prevalence and clinical picture of sleep paralysis in a polish student sample. Int J Environ Res Public Health. 2020;17:3529.
    [CrossRef] [PubMed] [Google Scholar]
  13. , , , , . The frequency and correlates of sleep paralysis in a university sample. J Res Pers. 1995;29:285-305.
    [CrossRef] [Google Scholar]
  14. , , , , , , et al. Comparative prevalence of isolated sleep paralysis in Kuwaiti, Sudanese, and American college students. Psychol Rep. 2004;95:317-22.
    [CrossRef] [PubMed] [Google Scholar]
  15. . Sleep paralysis in college students. J Am Coll Health. 2020;70:1286-91.
    [CrossRef] [PubMed] [Google Scholar]
  16. , , . A systematic review of variables associated with sleep paralysis. Sleep Med Rev. 2018;38:141-57.
    [CrossRef] [PubMed] [Google Scholar]
  17. . Relationships between sleep paralysis and sleep quality: Current insights. Nat Sci Sleep. 2018;10:355-67.
    [CrossRef] [PubMed] [Google Scholar]
  18. , . Hypnagogic and hypnopompic hallucinations during sleep paralysis: Neurological and cultural construction of the nightmare. Conscious Cogn. 1999;8:319-37.
    [CrossRef] [PubMed] [Google Scholar]
  19. . The neuropharmacology of sleep paralysis hallucinations: Serotonin 2A activation and a novel therapeutic drug. Psychopharmacology (Berl). 2018;235:3083-91.
    [CrossRef] [PubMed] [Google Scholar]
  20. , , , , , . Prevalence rates of the incubus phenomenon: A systematic review and meta-analysis. Front Psychiatry. 2017;8:253.
    [CrossRef] [PubMed] [Google Scholar]
  21. . "The devil lay upon her and held her down". Hypnagogic hallucination and sleep paralysis described by the Dutch physician Isbrand van Diemerbroeck (1609-1674) in 1664. J Sleep Res. 2008;17:464-7.
    [CrossRef] [PubMed] [Google Scholar]
  22. , , . Lucid dreaming, nightmares, and sleep paralysis: Association with reality testing deficits and paranormal experience/belief. Front Psychol. 2020;11:471.
    [CrossRef] [PubMed] [Google Scholar]
  23. . Self-perception in the case of sleep paralysis: A state of consciousness within the dream MOR. Rev Mex Neuroci. 2016;17:72-84.
    [Google Scholar]
  24. , . Sleep paralysis and psychopathology In: Sleep Paralysis. Historical, Psychological and Medical Perspectives. New York: Oxford University Press; . p. :620-93.
    [CrossRef] [Google Scholar]
  25. . Personality components in patients with sleep paralysis. Psych Quar. 1969;43:343-8.
    [CrossRef] [PubMed] [Google Scholar]
  26. , , , . Explanation of sleep paralysis among Egyptian college students and the general population in Egypt and Denmark. Transcult Psychiatry. 2014;51:158-75.
    [CrossRef] [PubMed] [Google Scholar]
Show Sections