emDOCs Wellness: Sleep and Shift Work

Author: Jennifer Robertson, MD, MSEd (Assistant Professor, Emory University School of Medicine) // Edited by: Alex Koyfman, MD (@EMHighAK) and Brit Long, MD (@long_brit)

Let’s face it, shift work can be brutal, and sleep disruption does not help. With the circadian rhythm disturbances of shift work, maintaining adequate sleep can be difficult (1).  Many factors may contribute to poor health in all physicians, including sleep deficits, poor diet, and lack of exercise. Unfortunately for emergency physicians, the circadian rhythm changes secondary to rotating shifts and night shifts may contribute to many adverse health consequences (1). Studies have demonstrated that shift work and sleep disruption may contribute to poor cardiovascular health, gastrointestinal diseases, obesity, diabetes mellitus, and even certain cancers (1,2)

Rotating shifts, night shifts, and the circadian rhythm

The quality of sleep and of cognition during waking hours is largely determined by the biologic circadian rhythm (3). From the circadian perspective, cognition is at its peak during the internal biologic day and sleep is optimal during the biologic night (3). However, the circadian rhythm (and its disruption) seems to affect many aspects of our physical health and not simply cognitive function (1).

The human circadian rhythm is complex, but it is largely regulated by the suprachiasmatic nuclei (SCN) in the hypothalamus, the pineal gland, and the retina (4). The SCN rely on outside “time givers” to help regulate their function. The main “time givers” include endogenous melatonin and the day-night cycle of the earth (4). Under regular conditions, the SCN neurons are reset daily by light inputs to the retina during the day as well as melatonin secretion via the pineal gland and diminished light inputs to the retina at night (4). Thus, melatonin secretion is at its peak at nighttime (4).

This cycle is quite regulated. Studies have shown that circadian oscillation creates time zones during the day where sleep rarely occurs, and time zones where sleep is nearly unavoidable (5). Thus, for those who work night shifts and have rotating shifts, regular sleep can be difficult to maintain because wake and sleep patterns are out of phase with the endogenous circadian clock. Consequently, even after several weeks of shift work, the circadian clock does not truly adapt if light is providing input about the time of day (6). Even purely working night shifts does not allow for adaptation. In fact, night shift workers are reported to result in a greater loss of total sleep time than evening and rotating shift workers (7). Assessment of sleep via electroencephalogram of rotating shift workers has found that day sleep is at least two hours shorter than night sleep (8). Thus, shift work, especially night shift work, can be detrimental to one’s sleep cycle.

So, the emergency medicine physician is chronically sleep deprived. So, what?

It is important to understand that our circadian cycle is more than just about sleep.  Influenced by, and from, our autonomic nervous system and various hormones, the circadian cycle has an underappreciated impact on human health (9). When the circadian cycle gets disrupted, more than simple fatigue can occur. It is thought that circadian disruption may lead to certain diseases because of the neural and hormonal changes that occur as a result of being awake during unusual hours of the day (9).

Epidemiologic studies in shift workers have suggested that these workers have disrupted cardiac autonomic function (10), abnormal cortisol levels (11), impaired carbohydrate metabolism, insulin resistance, obesity, higher rates of peptic ulcer disease and other gastrointestinal problems, hypertension, and a higher risk of developing coronary artery disease (1, 12, 13). Additionally, other studies have suggested that shift work is associated with a high risk of certain cancers, including prostate and breast cancers (2, 14). While the mechanisms of developing these diseases are not fully understood, it is thought that alterations in the autonomic nervous and hormonal systems that occur with circadian rhythm disruption may play roles (1, 13, 14, 15).

Getting enough sleep

Having an increased risk for obesity, diabetes, hypertension and cancer is scary. Certainly, lifestyle factors in shift workers also likely contribute to the development of these diseases processes including smoking, lack of exercise, and poor diet (16).  Thus, maintaining a proper diet and getting adequate exercise are extremely important for the shift worker and will hopefully be addressed in future EMDocs wellness articles.

However, as mentioned previously, adequate sleep is extremely important for maintaining health. While sleep cycles never fully adjust for most individuals, it is thought that some of the methods mentioned below may help mitigate some of the adverse effects impacted by circadian disruption.

1. Light manipulation

As previously mentioned, light is the principal synchronizer of the circadian rhythm. It helps train the circadian cycle by suppressing melatonin, elevating core body temperature, and increasing heart rate, which allows for improved alertness and overall functioning (17).  Because of these reasons, it is thought that perhaps manipulating light exposure may help workers adapt to unusual work schedules (17, 18).  In addition, it has been found that the human circadian rhythm can be reset best using specific wavelengths of light, namely between 460-480 nm (19).  Of course, light therapy should be appropriately timed (17, 18). Core body temperature varies during the 24- hour day and sleep normally occurs on the downward slope of the body temperature rhythm. Body temperature is typically lowest about two to three hours prior to awakening (20). It is recommended that workers try to receive several hours of intermittent bright light during their shifts for improved circadian phase delay (20, 21). Commercial light boxes or glasses can be obtained for this purpose (20). Overall, there are no known standard guidelines about the timing and application of light therapy (22). However, the American Academy of Sleep Medicine (AASM) does recommend using intermittent timed light exposure while working and light restriction in the morning, when feasible (23).

This brings us to another big issue. A significant cause of suboptimal adjustment to night shift work is the morning expose to natural sunlight. This sends a signal to the circadian pacemaker that prevents adequate sleep once arriving home after a shift (24). Thus, it has been recommended that shift workers wear protective eyewear, such as dark sunglasses, after working overnight shifts so that natural sunlight can be avoided (20). Blackout shades in one’s bedroom can also be extremely helpful for sleeping during daytime hours.

2. Scheduled naps

The AASM also recommends planned napping either before a night shift to improve alertness, performance, decreased sleepiness and decreased errors. The society indicates that planned nap during a shift will count as well, but typically most emergency physicians are unable to sleep during overnight shifts (23).

3. Melatonin

When administered in suitable doses and at correct times, melatonin has the ability to induce sleep and sleepiness and assist with changing circadian phases (25). Melatonin supplementation in doses of 0.5 to 10 milligrams (mg) prior to daytime sleep in night workers may help with sleep duration and quality, although the evidence is mixed (22, 23, 26, 27). In a recent 2015 Cochrane review of several pharmacologic sleep aids, Lira and colleagues found low quality evidence that taking melatonin (1-10mg) after an overnight shift may increase sleep length compared to placebo (26).  In a 2008 study, 5 mg of melatonin was compared to placebo in a randomized controlled trial of night shift nurses. The melatonin was administered 30 minutes prior to sleep. Overall, sleep onset latency was reduced in participants taking melatonin as compared to placebo. However, the authors found no difference in total sleep time as compared to baseline total sleep time.  No adverse effects were found due to the melatonin, and thus, while data remains limited in its efficacy, it still is recommended for use. The AASM does recommend for night shift workers melatonin supplementation in doses of 1.8-3 mg prior to sleep (23).

4. Other pharmacologic therapies

Other pharmacologic aids have also been evaluated in their abilities to regulate sleep. These include stimulants such as caffeine and modafinil and sleep aids such as zopiclone and other sedative hypnotics (23, 26). A 2015 Cochrane review by Lira and colleagues provides the best summary of evidence regarding these agents so far, but unfortunately, the data remains limited (26). Overall, the authors conclude that the stimulants armodafinil and modafinil, taken before night shifts, probably will modestly increase alertness and reduce sleepiness based on simple reaction time tests and psychomotor vigilance testing (26). Unfortunately, the authors also indicate that these medications come with adverse effects such as elevated blood pressure, headache, and nausea.  Naps plus caffeine also do reduce sleepiness during the night shift, but the quality of evidence is low (26). Of the sedative hypnotics, the authors only evaluated one randomized controlled trial (RCT) on zopiclone. Unfortunately, it was of low quality, and the medication was not found to significantly lengthen daytime sleep times compared to placebo (26).

On the other hand, the AASM does mention level one evidence (based on RCTs) that certain sedative hypnotic agents, namely triazolam and zopiclone, may be useful for night shift workers.

The authors note that these studies have “generally improved the quality of daytime sleep compared to controls”. However, the AASM notes that these medications have less clear evidence for improving nighttime alertness, and they may also worsen co-existing sleep conditions such as sleep apnea (23). Thus, the AASM recommends weighing risk versus benefit in the use of these medications

Regarding stimulants, the AASM does endorse the use of modafinil or caffeine to enhance alertness for night shift workers, based on level 1 evidence (23). The authors note that both drugs have established safety records and note that the benefits may outweigh the risks using them. However, the AASM indicates that one must be careful when using any stimulant agents so that they do not impair daytime sleep.

Finally, it should be noted that the AASM is only making these recommendations for those patients who suffer from shift work disorder (SWD). SWD is diagnosed by the presence of excessive sleepiness and/or insomnia for ≥1 month while an individual is performing shift work (23). It is uncertain how many workers actually meet criteria for SWD. In addition, there are individual differences in symptoms and thus, difficult to diagnose. It may, therefore, be difficult to know exactly who would benefit from these medications.

5. Work schedule design

It is generally accepted that for workers who rotate varying shifts, that a forward rotating schedule is superior to backward rotating schedule, mostly due to the larger amount of time between shifts (28, 29). There does not seem to be solid data on rapid versus slow forward moving schedules, but overall, it does seem to support forward, as opposed to backward, rotating shift schedules. Finally, and as previously mentioned, it should be remembered that solely working night shifts is not superior in terms of adequate sleep and circadian adjustment (7, 30).  Thus, perhaps forward rotating shifts are best in terms of overall total sleep and circadian adjustment. However, a small number of individuals seem to adjust better to night shifts than others and thus, further studies may be necessary to determine the best schedule for most (31).

 

Conclusions

Sleep disruption for the shift worker can be detrimental to one’s physical, mental, and emotional health. However, understanding the circadian cycle and initiating certain routines can be helpful toward mitigating the harmful effects of shift work. This may include properly timed light exposure, scheduled naps, melatonin and other pharmacologic therapies, and utilizing a forward shift schedule design. Shift work and the circadian cycle may never fully align, but there are tools available to help one cope with the demands and sleep disruption of shift work.

 

References / Further Reading:

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  2. Papantoniou K, Castaño‐Vinyals G, Espinosa A, et al. Night shift work, chronotype and prostate cancer risk in the MCC‐Spain case‐control study. Int J Canc 2015;137(5):1147-57.
  3. Åkerstedt T, Wright KP. Sleep loss and fatigue in shift work and shift work disorder. SleepMed Clin 2009;4(2):257-71.
  4. Richardson GS. The human circadian system in normal and disordered sleep. J Clin Psychiatry 2005; 66:3-9.
  5. Weitzman ED, Nogeire C, Perlow M, et al. Effects of a prolonged 3-hour sleep-wake cycle on sleep stages, plasma cortisol, growth hormone and body temperature in man. Int J Clin Endocrinol Metab 1974;38(6):1018-30.
  6. Knauth P, Rutenfranz J. Experimental shift work studies of permanent night, and rapidly rotating, shift systems. Int Arch Occup Environ Health 1976;37(2):125-37.
  7. Park YM, Matsumoto K, Seo YJ, Cho YR, Noh TJ. Sleep–wake behavior of shift workers using wrist actigraph. Psychiatry Clin Neurosci 2000;54(3):359-60.
  8. Torsvall L, Akerstedt T, Gillander K, et al. Sleep on the night shift: 24‐hour EEG monitoring of spontaneous sleep/wake behavior. Psychophysiology 1989;26(3):352-8.
  9. Buijs RM, Van Eden CG, Goncharuk VD, et al. The biological clock tunes the organs of the body: timing by hormones and the autonomic nervous system. J Endocrinol 2003;177(1):17-26.
  10. Chung MH, Kuo TB, Hsu N, et al. Sleep and autonomic nervous system changes—enhanced cardiac sympathetic modulations during sleep in permanent night shift nurses. Scand J Work Environ Health 2009; 35 (3):180-7.
  11. Munakata M, Ichii S, Nunokawa T, et al. Influence of night shift work on psychologic state and cardiovascular and neuroendocrine responses in healthy nurses. Hypertens Res 2001;24(1):25-31.
  12. Suwazono Y, Dochi M, Oishi M, et al. Shiftwork and impaired glucose metabolism: a 14-year cohort study on 7104 male workers. Chronobiol Int 2009;26(5):926-41.
  13. Wang F, Zhang L, Zhang Y, et al. Meta‐analysis on night shift work and risk of metabolic syndrome. Obes Rev 2014;15(9):709-20.
  14. Haus EL, Smolensky MH. Shift work and cancer risk: potential mechanistic roles of circadian disruption, light at night, and sleep deprivation. Sleep Med Rev 2013;17(4):273-84.
  15. Neufeld EV, Carney JJ, Dolezal BA, et al. Exploratory Study of Heart Rate Variability and Sleep among Emergency Medical Services Shift Workers. Prehosp Emerg Care. 2017;21(1):18-23.
  16. Knutsson A. Health disorders of shift workers. Occup Med 2003;53(2):103-8.
  17. Skene DJ, Arendt J. Human circadian rhythms: physiological and therapeutic relevance of light and melatonin. Ann Clin Biochem 2006; 43(5):344-53.
  18. Burgess HJ, Sharkey KM, Eastman CI. Bright light, dark and melatonin can promote circadian adaptation in night shift workers. Sleep Med Rev 2002;6(5):407-20
  19. Brainard GC, Hanifin JP, Greeson JM, et al. Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. J Neurosci 2001;21(16):6405-12.
  20. Kolla BP, Auger RR. Jet lag and shift work sleep disorders: how to help reset the internal clock. Cleve Clin J Med 2011;78(10):675-84.
  21. Boivin DB, James FO. Circadian adaptation to night-shift work by judicious light and darkness exposure. J Biol Rhythms 2002;17(6):556-67.
  22. Bjorvatn B, Stangenes K, Øyane N, et al. Randomized placebo-controlled field study of the effects of bright light and melatonin in adaptation to night work. Scand J Work Environ Health. 2007; 33 (3):204-14.
  23. Morgenthaler TI, Lee-Chiong T, Alessi C, et al. Practice parameters for the clinical evaluation and treatment of circadian rhythm sleep disorders. Sleep 2007;30(11):1445-59.
  24. Czeisler CA, Moore-Ede MC, Coleman RH. Rotating shift work schedules that disrupt sleep are improved by applying circadian principles. Science 1982;217(4558):460-3.
  25. Arendt J, Skene DJ. Melatonin as a chronobiotic. Sleep Med Rev 2005;9(1):25-39
  26. Liira J, Verbeek J, Ruotsalainen J. Pharmacological interventions for sleepiness and sleep disturbances caused by shift work. JAMA 2015;313(9):961-2.
  27. Sadeghniiat-Haghighi K, Aminian O, Pouryaghoub G, et al. Efficacy and hypnotic effects of melatonin in shift-work nurses: double-blind, placebo-controlled crossover trial. J Circadian Rhythms 2008;6(1):10.
  28. Pilcher JJ, Lambert BJ, Huffcutt Al. Differential effects of permanent and rotating shifts on self-report sleep length: a meta-analytic review. Sleep 2000; 23 (2): 155-63.
  29. Klein Hesselink J, De Leede J, Goudswaard A. Effects of the new fast forward rotating five-shift roster at a Dutch steel company. Ergonomics. 2010;53(6):0-38.
  30. Folkard S. Do permanent night workers show circadian adjustment? A review based on the endogenous melatonin rhythm. Chronobiol Int 2008;25(2-3):215-24.
  31. Costa G. The problem: shiftwork. Chronobiol Int 1997; 14(2):89-98

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