Shift work sleep disorder

Shift work sleep disorder (SWSD) is a circadian rhythm sleep disorder characterized by insomnia, excessive sleepiness, or both affecting people whose work hours overlap with the typical sleep period. Insomnia can be the difficulty to fall asleep or to wake up before the individual has slept enough. About 20% of the working population participates in shift work. SWSD commonly goes undiagnosed, so it's estimated that 10–40% of shift workers have SWSD. The excessive sleepiness appears when the individual has to be productive, awake and alert. There are numerous shift work schedules, and they may be permanent, intermittent, or rotating; consequently, the manifestations of SWSD are quite variable. Most people with different schedules than the ordinary one (from 8 AM to 6 PM) might have these symptoms but the difference is that SWSD is continual, long term, and starts to interfere with the individual's life. Low fertility and issues during pregnancy are increased in shift workers. Obesity, diabetes, insulin resistance, elevated body fat levels and dyslipidemias were shown to be much higher in those who work night shift. SWSD can increase the risk of mental disorders.

Sleep loss and decreased quality of sleep is another effect of shift work. To promote a healthy lifestyle, the American Academy of Sleep Medicine recommended that an adult have 7 or more hours of sleep per day. Each year, there are almost 100,000 deaths estimated in the U. S. because of medical errors. Having a lack of sleep can impact cognitive performance. Accidents in the workplace have been found to be 60% higher in shift workers.

Although SWD affects many shift workers, its manifestation is still unclear within the general shift working population. A field study investigating the nature of SWD in an experimental (with SWD) and control (non SWD) group of Finnish shift workers revealed decreased total sleep time (TST) and increased sleep deficit before morning shifts. In a study by Akkerstedt et al., those who had a hard time sleeping in the past two weeks were at a greater risk for having a fatal workplace accident (RR=1.89, 95% CI 1.22–2.94). Other sleep disorders, like OSA which are risk factors for SWSD, have also been associated with low productivity, absenteeism, and accidents. such as IL 6, and a decrease in anti inflammatory markers, such as IL 10, that plays a role in tumor suppression. Chronic shift work has been associated with decreased immune function in nurses. In a study by Naigi, et al., over the course of a shift, nurses exhibited decreasing levels of Natural Killer cells, an innate immune response that plays a role in infectious disease and tumor suppression. Other researchers have found that less sleep at night increased the risk of developing the common cold. A supporting study by Moher et al. showed that shift workers were more likely to develop infectious diseases after exposure compared to daytime workers. A poorly functioning immune system may leave workers vulnerable for developing occupational illnesses. Sleep loss is also associated with an increase in TNF, a marker of systemic immune functioning.

Decreased sleep quality and duration have also been associated with other chronic illnesses, such as cardiovascular disease. Many studies have shown that prolonged sleeplessness and sleep disorders, such as OSA, increases systemic levels of CRP, a marker of cardiovascular disease. Those with sleep disorders were also at a higher risk for being in a motor vehicle crash (OR=2.0 95% CI 1.29–3.12, p=0.0021), near crash (OR=2.49 95% CI 2.13–2.91, p < 0.0001), and nodding off while driving (OR=2.41 95% CI 2.06–2.82, p < 0.0001). However, SWSD is estimated to affect 2–10% of general population It may be that female night workers sleep less than their male counterparts.

Shift work sleep disorder affects many individuals, especially those within the medical field. Research done by The Journal Of Sleep Research examine the difference in cognitive function using sleep deprived and well rested nurses using autobiographical memory skills. The participants underwent the autobiographical memory test, as well as anxiety and depression inventories. The researchers found that a sleep deprived group of individuals scored significantly higher in the depression score and remembered more negative than positive memories. The sleep deprived group also scored significantly lower than the well rested group in autobiographical memory and specific memories. This study is similar to the one done by the National Center for Biotechnology Information, which found that their hypothesis of sleep deprivation and the cognitive impact it has on nurses was strongly supported in 69% of shift workers. The impairment in cognitive performance, such as general intellect, reaction time, and memory, was statistically significant among the staff nurses due to poor sleep quality and decreased alertness while awake.

Shift work sleep disorder affects patient care within all aspects of the medical field. Research published in European Review for Medical and Pharmacological Sciences analyzed the correlation between the clinical risk management and the occurrence of medication errors and the effects of the shift work on inpatient nurses. The researchers reviewed 19 out of 217 research articles and focused on the impact of workload, shifts and sleep deprivation on the probability of making medication errors. They found that the main reason behind medication errors are stress, fatigue, increased workload, night shifts, nurse staffing ratio and workflow interruptions.

Brain arousal is stimulated by the circadian system during the day and sleep is usually stimulated at night. The rhythms are maintained in the suprachiasmatic nucleus (SCN), located in the anterior hypothalamus in the brain, and synchronized with the day/night cycle. Variations in exposure can advance or delay these rhythms. For example, the rhythms can be delayed due to light exposure at night. The symptoms coincide with the duration of shift work and usually remit with the adoption of a conventional sleep wake schedule.

Experts agree that there is no such thing as an "ideal" night work schedule, but some schedules may be better than others. For example, rotating shifts every two weeks in a forward (delaying) direction was found to be easier than rotation in a backward (advancing) direction. Gradual delays ("nudging" the circadian system about an hour per day) has been shown in a laboratory setting to maintain synchrony between sleep and the endogenous circadian rhythms, but this schedule is impractical for most real world settings. Some experts have advocated short runs (1 to 2 days) of night work with time for recovery; however, in the traditional heavy industries, longer (5 to 7 day) runs remain the rule. In the end, scheduling decisions usually involve maximizing leisure time, fairness in labor relations, etc. rather than chronobiological considerations. Shift workers can benefit from adhering to sleep hygiene practices related to sleep/wake scheduling. In the transportation industry, safety is a major concern, and mandated hours of service rules attempt to enforce rest times.

The light dark cycle is the most important environmental time cue for entraining circadian rhythms of most species, including humans, and bright artificial light exposure has been developed as a method to improve circadian adaptation in night workers. The timing of bright light exposure is critical for its phase shifting effects. To maximize a delay of the body clock, bright light exposure should occur in the evening or first part of the night, and bright light should be avoided in the morning. Wearing dark goggles (avoiding bright light) or blue blocking goggles during the morning commute home from work can improve circadian adaptation. For workers who want to use bright light therapy, appropriate fixtures of the type used to treat winter depression are readily available but patients need to be educated regarding their appropriate use, especially the issue of timing. Bright light treatment is not recommended for patients with light sensitivity or ocular disease.

Melatonin is a hormone secreted by the pineal gland in darkness, normally at night. Its production is suppressed by light exposure, principally blue light around 460 to 480 nm. Light restriction, or dark therapy, in the hours before bedtime allows its production. Dark therapy does not require total darkness. Amber or orange colored goggles eliminate blue light to the eyes while allowing vision. Melatonin is also available as an oral supplement. In the US and Canada, the hormone melatonin is not classified as a drug; it is sold as a dietary supplement. In other countries, it requires a prescription or is unavailable. Although it is not licensed by the FDA as a treatment for any disorder, there have been no serious side effects or complications reported to date. Melatonin has been shown to accelerate the adaptation of the circadian system to a nighttime work schedule. Melatonin may benefit daytime sleep in night workers by an additional direct sleep promoting mechanism. Melatonin treatment may increase sleep length during both daytime and nighttime sleep in night shift workers.

Caffeine is the most widely used alerting drug in the world and has been shown to improve alertness in simulated night work. Caffeine and naps before a night shift reduces sleepiness during the shift. Modafinil and armodafinil are non amphetamine alerting drugs originally developed for the treatment of narcolepsy that have been approved by the FDA (the US Food and Drug Administration) for excessive sleepiness associated with SWSD.

Obtaining enough sleep during the day is a major problem for many night workers. Hypnotics given in the morning can lengthen daytime sleep; however, some studies have shown that nighttime sleepiness may be unaffected. Zopiclone has been shown to be ineffective in increasing sleep in shift workers.