Prevalence and Clinical Characteristics of Sleeping Paralysis: A Systematic Review and Meta-Analysis

Abstract

Sleep paralysis (SP) is a mixed state of consciousness and sleep, combining features of rapid eye movement (REM) sleep with those of wakefulness. The exact cause of SP is unknown, and its prevalence varies among the studies. We aim to identify SP's global prevalence, the affected population's characteristics, and the SP's clinical picture. We searched three databases (PubMed, Scopus, and Web of Science (WoS)) using a unique search strategy to identify eligible studies. All observational studies identifying the prevalence or frequency of sleeping paralysis were included. No exclusions are made based on country, race, or questionnaire. The analysis was performed using the latest version of R software (R Core Team, Vienna, Austria). The analysis included 76 studies from 25 countries with 167,133 participants. The global prevalence of SP was 30% (95% CI (22%, 39%)). There were similar frequencies of isolated SP and SP (33%, 95% CI (26%, 42%), I2 = 97%, P <0.01; 31%, 95% CI (21%, 43%), I2 = 100%, P = 0, respectively). A subgroup analysis showed that the majority of those who experienced SP were psychiatric patients (35%, 95% CI (20%, 55%), I2 = 96%, P <0.01). The prevalence among non-psychiatric patients was among students (34%, 95% CI (23%, 47%), I2 = 100%, P = 0). Auditory and visual hallucinations were reported in 24.25% of patients. Around 4% had only visual hallucinations. Meta-regression showed no association between the frequency of SP and sex. Publication bias was detected among the included studies through visual inspection of funnel plot asymmetry. Our findings revealed that 30% of the population suffered from SP, especially psychiatric patients and students. The majority of SP cases lacked associated hallucinations, while a noteworthy proportion experienced combined visual and auditory hallucinations.

Keywords: hallucinations; isolated sleep paralysis; isp; prevalence; ptsd; sleeping paralysis; sp.

Figure 1. PRISMA Flow Diagram

PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses

Figure 2. The overall prevalence of included studies

Figure 3. Subgroup analysis of SP and ISP

SP: sleep paralysis; ISP: isolated sleep paralysis

Figure 4. Subgroup analysis based on the prevalence of SP among populations

SP: sleep paralysis

Figure 5. Prevalence of SP according to the type of questionnaire

SP: sleep paralysis; WUSEQ: Waterloo Unusual Sleep Experience Questionnaire; USEQ: Unusual Sleep Experiences Questionnaire; SP-EPQ: Sleep Paralysis Experience and Phenomenology Questionnaire

Figure 6. Meta-regression based on the year of publication

Figure 7. Meta-regression based on sex

Figure 8. Meta-regression based on sample size

Figure 9. Funnel plot - Egger's test showing the probability of publication bias

Figure 10. Funnel plot - the trim and fill method showing the probability of publication bias