By Dr Nyasha Grace Gogoma

As humans harnessed electricity and artificial lighting, many industries saw it fit to remain operational 24/7, thus coming to rely heavily on shift workers to maintain round-the-clock service.^1,2 It is estimated that about one-fifth of the global population engages in shift work, and these employees are typically seen in the transportation, manufacturing, hospitality, and healthcare industries.^1,2,3 Shift work is typified by work performed in blocks that rotate and alternate between the morning, afternoon, and night periods. Employees who perform shift work are more likely to work outside the conventional working hours of 7 AM to 6 PM.^2,4

Nearly all organisms that call Earth home have adapted to a 24-hour day that begins around the same time each morning.^1,5 Through internal clocks known as circadian rhythms, living things coordinate their biological and behavioral functions with the external time environment.^1,5 Our circadian rhythm helps us wake up each morning, work during the day, and go to sleep at night on a predictable schedule. As inconvenient as the need for sleep might seem to many, quality sleep is critical for brain and whole-body health.⁶ For our minds and bodies to also function optimally, our body clock must be synchronized exactly to the external environment. Our internal rhythms naturally follow a cycle of about 24 hours, though if left to their own devices would run on a cycle slightly longer than 24 hours.^1,5 Therefore, the internal clock is reset to exactly 24 hours each morning by exposure to bright light through a process called circadian photoentrainment.^1,5

Night work, a special subcategory of shift work involving at least 3 hours of work between 11 PM and 6 AM, is particularly deleterious to health.³ Without intervention, the circadian rhythms of chronic night workers seldom phase shift in alignment with the sleep-wake pattern necessitated by their jobs.⁷ In other words, their bodies still expect them to sleep at night and be awake during the day though their work schedule demands the opposite.⁷ This occurs because they are still exposed to bright light upon leaving work in the morning.^1,7 As a result, long-term night workers are in a constant state of circadian misalignment which may manifest as excessive somnolence and micro-napping during wakefulness, and disturbed sleep or insomnia during sleep time.^2,5,7 In about a quarter of shift workers, these symptoms are severe enough to cause considerable distress and functional impairment, and may then indicate a condition called shift work disorder (SWD).^2,3 While the specific diagnostic criteria of SWD are beyond the scope of this article, shift workers experiencing chronic sleep deprivation and persistent sleep debt (the difference between how much sleep one needs versus how much sleep one gets) may be suffering from SWD and should seek medical attention.¹

In addition to circadian misalignment, workers who sleep during the day while working at night struggle to maintain a healthy work-life balance as they forego many opportunities for social and leisure activities.⁴ It comes as no surprise, then, that night shift workers are exposed to a number of mental and physical health issues. Studies show that shift and night work is linked to increased risk of heart disease, certain cancers, metabolic derangements, digestive disorders, and poor reproductive and mental health.^2,3 Shift and night work is also associated with adverse outcomes at the workplace such as accidents, sick leave, decreased job satisfaction, and high staff turnover.³

There is no single best solution to combat the functional and health issues arising from shift work.⁸ The first step should always be to attempt to reduce the volume of shift or night work performed.⁸ Since this is usually not possible, the next step is to attempt to prevent or minimize sleep derangements owing to shift work using any of or all the methods described below.^2,8

Adjusting shift schedules

Several components of shift workers’ schedules can be adjusted to optimize their functionality. Where possible, shifts should be rotated forwards rather than backwards and quickly rather than slowly.^2,8,9 As an extreme example, a schedule of 2 morning shifts followed by 2 evening shifts followed by 2 night shifts and then 2 days off allows for better sleep, wakeful alertness, and social engagement than a schedule of 7 night shifts followed by 2 days off followed by 7 evening shifts followed by 2 days off followed by 7 morning shifts.^2,8,9 Research also suggests that shift lengths should be ideally 10 hours or less, with overnight shifts being 9 hours or shorter. Morning shifts should begin later (7 AM vs 6 AM) and evening shifts should end earlier (10 PM vs 11 PM).^2,8

Phase-shifting through controlled light exposure

As previously mentioned, light, particularly short-wavelength or ‘blue’ light is the main cue the circadian system uses to synchronize our internal rhythms to the external environment.^1,5 Exposure to high-intensity, blue-enriched light during the first few hours of a night shift delays the sleep cycle so that workers can feel more alert during the night and start to feel sleepy early in the morning. For optimum results, bright-light exposure at night must be coupled with light avoidance in the morning after the shift. Employees should avoid light exposure by wearing dark sunglasses on the commute home, immediately entering a darkened room upon arrival, and going to sleep.^2,7 Some have suggested that frequent phase-shifting may be detrimental to health. However, this risk must be weighed against the risk of workers developing persistent sleep debt due to chronic sleep deficiency.⁷

Planned napping and caffeine consumption

Strategically timed naps can confer significant benefits to night shift workers. A nap taken shortly before a night shift or at the moment of peak sleepiness during the shift boosts employee alertness and performance.² To decrease the risk of entering deep sleep, which can cause temporary sleep inertia upon waking, naps should only be 20 to 30 minutes long.² Caffeine is a stimulant known to reduce sleepiness, promote brain performance, and even reduce errors. Low-dose caffeine may be consumed during the night shift to cope with periods of extended wakefulness but must be stopped at least 6 hours before the planned bedtime to preserve optimal sleep quality and duration.²

Cognitive behavioural therapy for insomnia (CBT-i)

CBT-i is the first-line therapy recommended for the treatment of insomnia in the general population.² Aspects of conventional CBT-i such as sleep restriction and maintenance of a regular sleep schedule may prove out of reach for shift workers with odd working hours and pre-existing sleep deprivation; however, CBT-i guidelines can be specifically tailored to shift workers.²

In conclusion, shift work forms the backbone of many modern industries, but it comes at a significant cost to workers. Employers, workers, and healthcare providers should all work together to prevent or minimize the harm that this type of work causes.

References:

1. Walker WH, Walton JC, DeVries AC, Nelson RJ. Circadian rhythm disruption and mental health. Translational Psychiatry. 2020;10(1). https://doi.org/10.1038/s41398-020-0694-0
2. Tout AF, Nicole, Sletten TL, et al. Current sleep interventions for shift workers: a mini review to shape a new preventative, multicomponent sleep management programme. Frontiers in sleep. 2024;3. https://doi.org/10.3389/frsle.2024.1343393
3. Pallesen S, Bjorvatn B, Waage S, Harris A, Sagoe D. Prevalence of Shift Work Disorder: A Systematic Review and Meta-Analysis. Frontiers in Psychology. 2021;12(638252). https://doi.org/10.3389/fpsyg.2021.638252
4. Torquati L, Mielke GI, Brown WJ, Burton NW, Kolbe-Alexander TL. Shift Work and Poor Mental Health: a Meta-Analysis of Longitudinal Studies. American Journal of Public Health. 2019;109(11):e13-e20. https://doi.org/10.2105/ajph.2019.305278
5. Brown RL, Robinson PR. Melanopsin—Shedding Light on the Elusive Circadian Photopigment. Chronobiology International. 2004;21(2):189-204. https://doi.org/10.1081/cbi-120037816
6. Medic G, Wille M, Hemels M. Short- and long-term Health Consequences of Sleep Disruption. Nature and Science of Sleep. 2017;9(9):151-161. https://doi.org/10.2147/nss.s134864
7. Burgess HJ, Sharkey KM, Eastman CI. Bright light, dark and melatonin can promote circadian adaptation in night shift workers. Sleep Medicine Reviews. 2002;6(5):407-420. https://doi.org/10.1053/smrv.2001.0215
8. Knauth P, Hornberger S. Preventive and compensatory measures for shift workers. Occupational Medicine. 2003;53(2):109-116. https://doi.org/10.1093/occmed/kqg049
9. Sallinen M, Kecklund G. Shift work, sleep, and sleepiness – differences between shift schedules and systems. Scandinavian Journal of Work, Environment & Health. 2010;36(2):121-133. https://doi.org/10.5271/sjweh.2900