In the case of two patients, sleep deprivation seemed to increase the frequency of their sleep paralysis events.

Whether for a shiftworker, a world traveler, or a medical student who has just completed a 24-hour shift, isolated sleep paralysis (ISP) may cause frightening symptoms. For those who have not experienced ISP, it is an inability to perform voluntary movements at either sleep onset or awakening.1 The immediate awareness of a person experiencing ISP is of wakefulness but without the ability to move limbs, trunk, or head.2

Such muscle atonia causes alarm in people who do not understand what exactly is happening. Episodes occur most commonly while in the supine position, and some people report feeling progressively heavier as muscle atonia develops. In Terrillon and Bonham’s account of recurrent ISP, many people also report auditory and hallucinatory experiences. These experiences are consistently reported to be quite vivid and realistic and even include the experience of a phantom-like presence in the room or on the person.2

Case One
A 36-year-old Caucasian male presented with a complaint of ISP with vivid hallucinatory experiences and imagery that disturbed his sleep quite regularly. The patient’s history included regular night shift work and a routine daytime sleep period in which he did not experience problematic awakenings. Night shifts were from 7 pm to 8 am, and the normal sleep period for the man was from 9 am to 4 pm on work days. On off-shift days, his normal sleep period was from about 3 am to 9 am.

Additional physical history included a height of 72 inches, a weight of 208 pounds, a blood pressure of 126/80, and normal routine laboratory values. He did have a history of smoking and presently consumed moderate amounts of caffeine and alcohol. Daily ingestion of caffeine was three to four cups of coffee and, on his days off only, he consumed alcohol in moderation. He did not use sleep aids such as prescription medications, over-the-counter medications, and herbal supplements. He denied using recreational or illegal drugs as well. As an adult, he had a positive PPD (purified protein derivative) test for tuberculosis, and, as a child, he had surgery for tonsillectomy and adenoidectomy, as well as excision of his wisdom teeth. In addition, he had had Osgood Schlatter disease as a preteen, recurrent sinusitis, and a deviated septum.

He reported that his sleep was regular and restorative, both on and off his work schedule. A polysomnogram (PSG) detected no snoring, obstructive sleep apnea, or other limb movements. Not observed on the PSG, but reported by the patient was a history of somnambulism and somniloquy, as both a child and an adult.

His Epworth sleepiness score was 8, and he reported that he had sleep paralysis both during and off his work schedule. However, he said the majority of the ISP episodes occurred on his first day off during nocturnal sleep. He denied having a television, radio, or other external stimuli in his bedroom, and he estimated that his usual sleep latency was about 10 minutes. He could recall dreams during both daytime and nocturnal sleep, and he could usually recall any sleep paralysis episodes.

During episodes of sleep paralysis, the described imagery was of himself, suspended upside down, spinning and moving diagonally up to the corner of the bedroom, while simultaneously being able to see himself in the bed below. Not all episodes were accompanied by imagery, but, for those that were, the imagery was the same. All experiences resolved spontaneously within what he thought was just a few minutes and occurred about once every other week. Though he routinely reported sleep paralysis while working nights, he has since begun working day shifts and the frequency of his sleep paralysis has changed to only two to three times per year.

Case Two
An 18-year-old Caucasian girl presented in a neurology clinic with complaints of sharp pain in the back of her head and poor unrestorative sleep. The patient reported having severe sharp pains in the occipital region that lasted for about a minute. She also reported having throbbing and dull headaches in the same area. Sometimes the headaches were associated with phonophotophobia, but without nausea or vomiting. She attended college and had four to five such headaches in a 6-week period. Some mornings she would awaken with a headache. These headaches appeared to be unrelated to her menstrual period. She would go to bed between midnight and 1 am, but sometimes she would not fall asleep for up to an hour. She rose at 7 am for school. Although she denied weekday, daytime napping, she said she would occasionally nap for 20 minutes on weekends. She also said that her headaches had no relationship with food intake or sleep, and she stated that she had no stress from her college work. However, she also reported that there was no “quiet” time in her dormitory.

Her medical history revealed that her mother had nocturnal noise levels in the pregnancy. Her birth weight was 7 pounds and 7 ounces and, at the time of her birth, her mother was a 28-year-old gravida 1, para 0, abortus 0. There were no neonatal difficulties and she was without jaundice at her birth. Furthermore, the birth occurred at a sizable acute care facility with good obstetric care. Her development was considered entirely normative, although, as an infant, she had recurrent ear infections.

Physical and neurological examinations were completely normal. Computed tomographic images of her head and brain revealed no abnormalities, and she was free from evidence of sinus infection. Since her family history was strongly positive for migraine headaches, she was treated as having migraines.

Two sleep logs were obtained from the patient. One was obtained during a holiday time, and the other was recorded during a spring break. The sleep logs strongly suggested delayed sleep phase syndrome. Chronal therapy was inconvenient for the patient, but phototherapy was carried out with partial success. In addition, a mild hypnotic was prescribed to improve her sleep.

At this time she also reported having spells of inability to move while trying to fall asleep and when waking up from sleep. During these periods, she had complete awareness of her surroundings, but was unable to move even her fingers or feet. She was also unable to talk. Her spells of sleep paralysis usually occurred after periods of sleep deprivation.

At follow-up visits, she was encouraged to follow better sleep hygiene and develop a more regular routine for her getting in bed and awakening times. Subsequent office visits revealed that her sleep paralysis became infrequent once she improved her sleep hygiene.

In summary, this young woman had delayed sleep phase syndrome, sleep deprivation, and migraine headaches. Sleep logs revealed delayed bedtimes and that, when she was forced to get up in the morning for school, she did not get enough sleep. If she were allowed to sleep in, as shown in her spring break sleep log, she would sleep until noon and also make up for lost sleep time by napping in the afternoon. On Saturday and Sunday nights, she usually went to bed later. That might have been the cause of her sleep paralysis secondary to sleep deprivation.

Discussion
In these two cases, sleep deprivation and changing sleep schedules appear to be significant triggering mechanisms for ISP. The night shift worker’s incidence of sleep paralysis noticeably decreased with time; the longer he spent on first shift (with its established and less variable sleep periods), the less frequent the episodes became. The young woman in case two adopted better sleep hygiene and subsequently reported far less frequency of her sleep paralysis with every office visit thereafter.

The experience of sleep paralysis following periods of sleep deprivation and irregular sleep habits is consistent with results of an observational study done on ISP in health care employees that appeared in the winter 2001 issue of Sleep Review.

The survey and report demonstrated an unmistakable connection between these two influences on ISP. In the survey, 64 registered nurses completed a questionnaire that asked if they had ever experienced symptoms or periods of sleep paralysis. Of those polled, 18% of the first shift nurses reported having had ISP and 34% of the night or rotating shift nurses reported ISP.

Summary
For people without a regular sleep schedule or who must work nights and rotating shifts, the advice to make sleep a priority in life cannot be overstated. We know that these lifestyles and work schedules may contribute to sleep paralysis, and, though much about ISP is still not understood, we can impact its incidence.

Over the years, sleep paralysis has fascinated many of us in sleep medicine due to the demands of our roles in health care and the fact that so many of us are sleep deprived. Most clinicians have worked nights and irregular hours at some point in their careers and appreciate the challenges of balancing it all with the need for restorative sleep. For readers who have tried in vain to correct and improve the quality of their sleep, please consult a sleep specialist today. There is help.

Robert L. Lindsey, MS, RPsgT, is the director of neuromedical services and Lawrence T. Ch’ien, MD, DABSM, is a pediatric neurologist with the Regional Sleep Centers, Memorial Health Care System in Chattanooga, Tenn. Lindsey contributed case one and Ch’ien contributed case two.

References
1. Chokroverty S. Sleep Disorders Medicine. 2nd ed. Woburn, Mass: Butterworth & Heinemann; 1999.
2. Terrillon J-C, Marques-Bonham S. Recurrent isolated sleep paralysis [abstract and article]. Available at: http://www.theconsciousdreamer.org. Accessed March 2000.