How does shift work affect your body clock?

Short answer: Shift work asks you to work when your body clock expects sleep and to sleep when it expects daylight and activity. As a result, night workers usually sleep less, and less well, than day workers. Light timing, a dark and quiet bedroom, naps and forward-rotating schedules can ease the strain.

Does shift work affect sleep?

Yes. NIOSH, the US workplace health institute, notes that night shift workers usually get less sleep overall than day shift workers, and poorer-quality sleep. In a nationally representative US study of 6,338 adults, insomnia was reported by 18.5% of night-shift workers, compared with 8.4% of day workers. NIOSH adds that the drowsiness, fatigue and body clock disruption that come with too little or broken sleep are associated with immune problems, diabetes, cardiovascular disease and other long-term conditions.

Day sleep is hard because the body clock pushes for wakefulness in daylight. If your rhythm has not adjusted, there is only a short window after a night shift before your natural alerting signal kicks in, so the more sleep you get before 2 p.m., the better rested you will be.

What is shift work sleep disorder, and is it real?

It is real. The US National Heart, Lung, and Blood Institute lists shift work disorder as a type of circadian rhythm disorder. It affects people who work at night or on a rotating schedule and cannot get uninterrupted, good-quality sleep when their body needs it. It can cause insomnia, extreme tiredness, and sleepiness while working at night.

The same list includes jet lag disorder, which is often a temporary version of the same mismatch; see how long jet lag lasts.

What helps night shift workers sleep?

NIOSH training on shift work suggests:

• Go straight to bed when you get home, and sleep as long as you can.
• Make the bedroom very dark, so dark you cannot see your hand in front of your eyes, or wear an eye mask.
• Block noise with earplugs or white noise, and stop the phone from waking you.
• Take a nap before going back to work if you can.
• Seek bright light in the earlier half of the shift and less light in the later half. Wear sunglasses home only if someone else drives, since they can make drowsy driving worse.

Which shift schedules are easier on the body clock?

Forward rotation, for example moving from day shifts to evening shifts, is easier to adjust to than rotating backward. NIOSH training also cites advice to leave at least 11 hours between two shifts, and it calls a weekly rotation the most difficult speed of rotation.

Very early starts, at 6 a.m. or earlier, tend to shorten sleep. For why steady timing matters in general, see why sleep regularity matters.

When should a shift worker see a doctor?

Occasional bad nights are not a cause for concern, but persistent sleep problems should not be ignored. Talk to a doctor if poor sleep or sleepiness at work keeps going despite good habits, or if you struggle to stay awake on the drive home. Another sleep disorder, such as insomnia or obstructive sleep apnea, can make good sleep impossible even with careful coping strategies.

How Actogram looks at this

Irregular rhythms are a design goal for Actogram, a MedTech company whose focus is the body clock. It reads the daily rhythm of rest and activity from ordinary minute-level step counts from a phone or watch, and it aims to work for irregular days, such as shift work, jet lag and fragmented days. It reads the rhythm from the daytime activity pattern, not only from night sleep. Today its tools are for research and wellness use and do not diagnose, treat or prevent any condition.

Sources

• Shift Work and Sleep, NIOSH Science Bulletin, 2016
• Coping with the Night and Evening Shifts: Sleep, NIOSH, 2020
• Coping with the Night and Evening Shifts: Light, NIOSH, 2020
• Work Organization Strategies to Promote Alertness and Health in Nurses, NIOSH, 2020
• Do You Have Symptoms of a Sleep Disorder?, NIOSH, 2020
• Circadian Rhythm Disorders: Types, National Heart, Lung, and Blood Institute, 2022

General information, not medical advice. If sleep or tiredness problems affect your daily life, talk to a doctor. Reviewed 6 November 2026 by the Actogram team.