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Shift work and health
Night work and rotating shifts disrupt the biological clock, and so increase fatigue, accidents, sleep disorders, digestive and metabolic problems and heart disease – so shifts are planned by chronobiological principles and individual suitability for night work is assessed.
Why it matters in the exam
Items on this topic ask about shift work disorder – insomnia or excessive sleepiness linked to working hours and lasting at least three months – and about its health consequences: work accidents and road accidents on the way home, obesity, type 2 diabetes, heart disease, digestive disorders, poorer pregnancy outcomes, and worsening of conditions such as epilepsy and insulin-treated diabetes. The International Agency for Research on Cancer (IARC) has classified night work as "probably carcinogenic" to humans (group 2A). Other items ask about shift design: forward rotation (morning, evening, night) is better than backward rotation, a limited number of consecutive nights, enough rest between shifts, and a short planned nap. Personal measures are also tested: bright light at the start of the night shift, sunglasses on the way home, a dark, quiet bedroom by day, and low-dose melatonin before daytime sleep in some cases. In fitness assessment the question is which worker is less suited to night work – for example a worker whose epilepsy worsens with sleep loss or with poorly controlled diabetes – and the answer is individual assessment, not blanket exclusion. Remember that the greatest danger is reduced alertness in the late night hours, when the biological clock is at its low point.
Key points
- Night work disrupts the biological clock and increases accidents and disease.
- IARC has classified night work as "probably carcinogenic" (2A).
- Forward rotation and few consecutive nights are preferred.
- Bright light at the start of the shift and darkness for daytime sleep help adaptation.
- Suitability for night work is decided individually.
Summary table
| Aspect | What happens | What is done |
|---|---|---|
| Biological clock | Mismatch between working hours and the internal clock | Light at the start of the shift, darkness for daytime sleep |
| Sleep and fatigue | Short, broken daytime sleep, low alertness late at night | A planned nap, limiting consecutive nights |
| Accidents | Errors at work and accidents on the drive home | Avoiding drowsy driving, transport, rest before driving |
| Metabolic and cardiac | Obesity, diabetes, hypertension, heart disease | Monitoring risk factors, diet and activity |
| Cancer | Night work is classified as "probably carcinogenic" (2A) | Research and reducing night work where possible |
| Shift design | Forward rotation is better, rest between shifts | Morning, evening, night – not the reverse |
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Sources
- LaDou & Harrison, CURRENT Diagnosis & Treatment: Occupational & Environmental Medicine, 6th ed., 2021 — Shift work and sleep
- IARC Monographs, Night Shift Work (volume 124), 2020 — Evaluation of carcinogenicity of night shift work
- American Academy of Sleep Medicine, International Classification of Sleep Disorders, 3rd ed., text revision, 2023 — Shift work disorder
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.