An observational study of the incidence of isolated sleep paralysis in health care workers  shows that it may be managed through balancing circadian rhythms, sleep, and social  factors

Those of us actively working in the field of sleep medicine know that sleep paralysis is one of the problems associated with narcolepsy; however, isolated sleep paralysis (ISP) is a phenomenon that occurs in as many as 30% to 50% of normal humans.¹

During episodes of ISP, polysomnographic recordings show what appear to be transitions into or out of rapid eye movement (REM) sleep. As with REM atonia, the sufferer cannot perform voluntary movements. These episodes of transition are usually at sleep onset (hypnagogic or predormital) or upon awakening (hypnopompic or postdormital).¹

ISP experiences may cause feelings of fright, anxiety, and even a form of “double consciousness,” but they are usually of short duration. Episodes can spontaneously disappear or can be reversed by touch from another person.¹ The experience of double consciousness varies from person to person but does present with the recurrent theme of the person recalling fragments of dream imagery that have been superimposed on the environment.¹

The occasional incidence of ISP can be triggered by inconsistent sleep habits, travel that involves crossing multiple time zones, frequent jet lag, rotations of work schedules experienced by medical residents, and working shifts on a rotation.¹

The latter is of special interest to us as care providers and others who routinely perform shift work. Most clinicians who have worked nights know that it can be challenging and sometimes very difficult to adjust to day sleeping. Additionally, the responsibilities of family or personal business often require that we function in daylight hours. The combination of having to sleep during day hours, work night hours, and also balance personal business can lead to inconsistent sleep patterns for those working nights. Through formal and informal observation, personal experience, and now an observational survey, this article presents ISP as a phenomenon of sleep in both normal humans as well as shift workers.

Survey
A recent survey of 64 registered nurses was administered to collect data on the incidence of ISP among shift workers vs nonshift workers. The survey was completed by 32 day shift and 32 night shift or swing shift nurses. The survey asked respondents to first answer whether or not they thought they had experienced ISP based on a provided definition.

The respondents who answered positively then completed additional questions that asked them to describe their experience(s) with ISP. In three sections of the survey, nurses were asked to provide demographic data (Section I), list medicines taken at the time of ISP episodes, when the episodes occurred (Section II), and, in Section III, a more detailed description of the incidents that included frequency of ISPs, their duration, and length of average sleep time.

Data
The gender mix of the respondents was 52 female nurses and 12 male nurses (shown in Figure 1).

Further examination of the sample data shows that 19% of respondents were male and 81% were female. This gender ratio actually represents more males than the number who work at this particular hospital; however, this survey was completed by respondents who were selected based only on their shift. Selecting respondents by shift allowed us to look at responses of those who would be considered to work and sleep more normal hours versus nurses who work nights or a swing shift. The differences in incidence of ISP were reported between the two shifts (Figure 2, page 20).

Discussion
As one may expect from night workers’ sleep habits, they proportionately had a greater incidence of ISP as a percentage of their shift (of the total 32 nurses/shift ). On the first shift, the six positives represent 18.75% of the shift, while the night shift reported 11 of 32 nurses having at least one episode of ISP (34.3%).

At the time of our survey, we asked Vincent A. Viscomi, MD, diplomate, American Board of Sleep Medicine, Rochester, Minn, to comment on ISP in shift workers and whether improved sleep hygiene may help.

“Shift workers will clearly have ISP more frequently than those not working odd hours, and sleep hygiene certainly is important because good sleep hygiene will improve sleep efficiency. I do think that it is worrisome to patients who have symptoms associated with a dreamlike state, particularly if they are troubling to a patient (such as nightmares or hypnagogic hallucinations), because then you have a negative reinforcement to sleep. This could thereby contribute to sleep onset insomnia in that situation,” Viscomi says.

The same recommendations (listed below) that sleep professionals share with their own patients apply when helping a day sleeper cope with occasional periods of ISP.²

• avoid naps;
• restrict the sleep period to the average number of hours that were actually slept the preceding week;
• perform daily exercise at least 6 hours before bedtime;
• take a hot bath at least 2 hours before bedtime;
• maintain a regular amount of time out of bed 7 days per week;
• avoid exposure to bright light if woken up during the sleep period;
• get at least 30 minutes of sunlight within the first half hour of wake time;
• do not smoke close to bedtime;
• limit caffeine—especially within 6 hours of bedtime;
• limit alcohol use within a few hours of bedtime;
• keep clocks facing away from the bed;
• avoid strenuous exercise within 5 to 6 hours of bedtime;
• do not eat or drink heavily within 3 hours of bedtime;
• keep the bedroom dark, quiet, cool, and well ventilated;
• practice keeping the same bedtime ritual;
• in short sentences, list problems and steps for beginning the next day or night;
• learn simple self-hypnosis if you wake up at night;
• use stress management techniques during work hours;
• avoid unfamiliar sleep environments;
• be sure the mattress is of desired firmness;
• take an occasional sleeping pill if needed after consulting with a physician; and
• use the bedroom only for sleep—do not work or watch television in the bedroom. If possible, make arrangements for child care while you are asleep.²

Conclusion
The ability of any shift worker to successfully cope with the odd hours of work and sleep depends on maintaining a fine balance of three mutually interactive factors that include circadian rhythm, domestic concerns, and sleep.³

“Shift work problems can be understood by using a multifaceted approach that recognizes the interaction of circadian rhythms, sleep, and social and domestic factors in determining shift work coping ability.”⁴

Coping with ISP can be as easy as improving one’s sleep hygiene, or in the case of a person whose hypnagogic hallucinations become a negative reinforcement to sleep, medical treatment may be necessary.

Robert L. Lindsey, MS, RPSGT, is administrative codirector, and Paula G. Williams, MA, CRTT, RPSGT, is a night supervisor, both at the Regional Sleep Center and Neuromedical Services, Memorial Hospital, Catholic Health Initiatives, Chattanooga, Tenn.

References
1. Chokroverty S. Sleep Disorders Medicine. 2nd ed. Woburn, Mass: Butterworth & Heinemann; 1999.
2. Zarcone VP Jr. Sleep hygiene. In: Kryger MH, Roth T, Dement WC, eds. Principles and Practice of Sleep Medicine. 3rd ed. Philadelphia: WB Saunders; 2000:660.
3. Tepas DI, Carvalhais AB. Sleep patterns of shiftworkers. Occup Med. 1990;5:199-208.
4. Monk TH. Shift work. In: Kryger MH, Roth T, Dement WC, eds. Principles and Practice of Sleep Medicine. 3rd ed. Philadelphia: WB Saunders; 2000:605.