The effects of shift work on our health & performance

Medicine comes with a lot of challenges, one of them being shift work. We’ve all done many weeks of nights, weekends, evenings, public holidays. It can start to feel exhausting.

But what exactly are the effects of shift work on our mental and physical wellbeing? The science states that shift work can be detrimental to our health, with even longterm effects. Let’s take a closer look. 

The science – we can’t stop our circadian clock

Humans are born with a circadian clock, an inbuilt sleep-wake cycle.(1) It keeps you awake during the day, and asleep for about 8 hours during the night. Temperature, digestion, heart rate and blood pressure are all in tune with this circadian rhythm.(1-4)

Night workers or those that start their shifts before 6am work counter to this circadian rhythm.(5) We have a marked circadian preference for sleep at night and even under optimal conditions, being awake at night is associated with impaired performance.(6) Diurnal rhythm of alertness and the drive to sleep are basic physiological processes – our commitment to our job doesn’t affect physiology.(6) Money and promotions do not reduce fatigue either.

This disruption to our circadian rhythm can also lead to an accumulation of sleep debt that is difficult to recover. Sleep professor Derk-Jan Dijk believes that even days off cannot fully recuperate this sleep debt, urging night shift workers to proactively sleep before a shift or nap during.(7)

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Effects of fatigue on work

The effects fatigue on performance are well defined, it leads to reduced concentration, data processing, and even affects short-term memory.(6) Fatigue also leads to increased variability of performance, with a bigger mix of great decisions with lapses of judgement.(6)

Fatigue mistakes aren’t usually prescribing the wrong antibiotic but something more disastrous, like failing to recognise the existence of a serious problem.(6) Research has proven that fatigue-related errors of judgement are difficult to prevent and often disastrous.(6)

There has been a myth spread that “doctors and army officers are the only occupational groups unaffected by fatigue”.(6) This is not the case, with even doctors requiring sleep to function at their best.

Sleep debt consequences (8):

  • Reduced immune function
  • Metabolic dysregulation and weight gain
  • Greater risk of falls and accidents
  • Increased risk occupational accidents
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The length and timing of shifts matters

It’s proven that long night shifts are worse than short ones, eight hour shifts are optimal.(6) Twelve hour shifts are acceptable only if the workload is light.(6)

Longer shifts lead to reduced productivity and more accidents.(6)

Night shifts often don’t end at 8.30am, they often extend into the morning for hand-over rounds and morning report.

“It’s expected I present an entire ward round (usually until 10.30-11am) after a night shift beginning at 8.30pm. Follow by a 45 minute-1 hour drive home. I feel so dangerous every time. When I get the train to help prevent crashing, I barely get six hours sleep. We need taxi vouchers or provide us onsite accommodation.”

Anonymous registrar

Working long shifts (>8 hours) and night shifts increases our risk of motor vehicle accidents.(6) Driving home can be the most dangerous thing we do as health professionals.(8)

It takes a person, on average, 10 days to adjust to night shifts.(9) Rotating between days and nights can aggravate the disruption to our natural rhythm. Thus making our sleep, metabolism, and digestion off kilter.

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Can we just get used to it?

Physiological adaptation to night work is a myth, so there is no reason to extend periods of night work in the hope that adaptation will occur.(6)

Though we may become more veteran in our shift work, studies show that sleep quantity may increase but quality of sleep does not.

Even staff who worked night shifts for years were found to have negative effects on sleep health and circadian rhythm.(10-11) Evidence shows that the more years you work nights the more disrupted your rhythm becomes!

Progressive sleep loss of a seven night roster causes a progressive rise in accidents and a fall in productivity.(6) Sleep deficits cannot be repaired immediately and after seven nights the accumulated sleep deficit is about 15-20 hours.(6)

Is it really that bad?

“I think there’s a misunderstanding that night-shift work is just an inconvenience, whereas it can be linked to serious health risks. We can’t avoid shift work for many professions, like healthcare workers, so we should be thinking about what can be done in terms of real-world adjustments to improve working conditions and schedules of shift workers. A better understanding of the biological mechanisms helps to find answers to this question.”(11)

Dr Julia Brettschneider of the University of Warwick Department of Statistics

Shift work has well-known immediate effects, but it also has been linked to longterm health issues.

Shift workers are more likely to develop (9):

  • Obesity
  • Cardiovascular disease
  • Mood changes
  • Gastrointestinal problems
  • Cancer, especially breast cancer – the World Health Organization classified shift work as a probable carcinogen in 2007
  • Sleep problems – little or disrupted sleep means the body never ‘powers down’, leading to lack of rest and recuperation
  • Relationship problems, including divorce

It may even shorten our life span.(9,12)

What now?

We need to minimise the risk of shift workers and maximise our health. Hospitals must stop staff from working dangerous hours and prevent them choosing to do so.(6)

“Heroic workloads are out of place in the routine organisation of the urban teaching hospital”.

Leslie G Olson and Antonio Ambrogetti – Working harder – working dangerously? (6)

Minimise risk

  • Nap pods
  • Taxi vouchers
  • Accomodation
  • Safe rostering *
  • Adequate time between nights and days to recover
  • Rethink current hours as 7pm-7am is considered the worst time for our cognitive functioning
*Safe rostering
  • Shorten night shifts 8 hours or less – do not exceed 12 hours
  • Don’t work >16 hrs
  • Limit consecutive night shifts to 2-3 shifts
  • 24 hours off every 2 night shifts
  • Avoid on call shifts followed by a normal working day

Maximise health

  • Develop a schedule to maximise our sleep
  • Rotate short naps on shift with colleagues (20-45 minutes)
  • Eat regular small meals
  • Avoid caffeine late in your shift
  • Sunlight before shift starts
  • Hydrate
  • Make time for movement
  • Avoid bright lights/screens after finishing night shifts

Stay tuned for tips on maximising sleep on nights.

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  1. Tunajek S. Working on the Night Shift: An Emerging Health Risk?. AANA Journal. 2007 Jun 1;61(6):32.
  2. Refinetti R, Menaker M. The circadian rhythm of body temperature. Physiology & behavior. 1992 Mar 1;51(3):613-37.
  3. Segers A, Depoortere I. Circadian clocks in the digestive system. Nature Reviews Gastroenterology & Hepatology. 2021 Apr;18(4):239-51.
  4. Coca A. Circadian rhythm and blood pressure control: physiological and pathophysiological factors. Journal of hypertension. Supplement: official journal of the International Society of Hypertension. 1994 Jul 1;12(5):S13-21.
  5. Boivin DB, Boudreau P. Impacts of shift work on sleep and circadian rhythms. Pathologie Biologie. 2014 Oct 1;62(5):292-301.
  6. Working harder – working dangerously?, in Medical Journal of Australia, vol. 168, pp. 614–616. More information here.
  7. Rimmer A. Doctors should nap during night shifts, conference hears.
  8. Spiegel K, Leproult R, Van Cauter E. Impact of sleep debt on metabolic and endocrine function. The lancet. 1999 Oct 23;354(9188):1435-9.
  9. Shiftwork, Better Health Channel, Victoria State Government Department of Health.
  10. Zhang Y, Cordina-Duverger E, Komarzynski S, Attari AM, Huang Q, Aristizabal G, Faraut B, Leger D, Adam R, Guénel P, Brettschneider JA. Digital circadian and sleep health in individual hospital shift workers: a cross sectional telemonitoring study. EBioMedicine. 2022 Jul 1;81:104121.
  11. Wise J. Sixty seconds on . . . power naps. BMJ : British Medical Journal (Online) 2022 Jun 09;377.
  12. Monk, T. H. (1997). Shift work. In M. R. Pressman & W. C. Orr (Eds.), Understanding sleep: The evaluation and treatment of sleep disorders (pp. 249–266). American Psychological Association.

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