Shift work and light: what is proven and what is not

Why is night shift work hard on your body clock?

Your body clock can change gradually, but most people’s clocks resist the sudden changes a shift rota asks for. Adjusting may take days or weeks, and even on permanent nights the clock never fully adjusts. Night workers who go back to a daytime routine on days off keep living with a disrupted clock (HSE, 2006).

Daylight is the cue that is hardest to control. The HSE notes that bright light at dawn after a night shift may make you less inclined to sleep (HSE, 2006).

The same clock gap after a long flight: jet lag and light.

What have light studies with night workers tested?

The studies we checked pair light at work with darkness afterwards, or pool many trials of light at work:

• Eastman et al., 1994: 50 people on a schedule of night work and day sleep. Bright light of about 5,000 lux for 6 hours on the first 2 night shifts plus dark goggles in daylight shifted the body clock the most. Dim light without goggles shifted it the least.
• Boivin & James, 2002: nurses on permanent nights. At work they got 6 hours of intermittent bright light (about 3,243 lux), and tinted goggles shielded them from bright morning light outdoors. Their body clock shifted about 9 hours later, against about 4 hours in nurses without the plan.
• Smith et al., 2009: 19 healthy adults on simulated night shifts from 23:00 to 07:00. They got four 15-minute bright light pulses per shift, wore dark sunglasses outside, slept in a dark bedroom at set times and went out into afternoon light as a “light brake”, so the clock would not drift too far.
• Wu et al., 2022: a meta-analysis of 14 studies with 621 shift workers. Pooled, sleepiness ratings were lower with the light setups. Only 5 of the 14 studies found a clear effect on their own, and the results varied a lot (I² = 78%).

Bright light during the shift: what is known

In the Wu meta-analysis, blue-enriched white light of 5,000 kelvin or more lowered sleepiness ratings across 8 studies. Warmer light was tested in only 3 studies, and that result was not clear. The authors rate the quality of the studies as moderate and call for larger, more rigorous trials (Wu et al., 2022).

The UK Health and Safety Executive lists “keep the light bright” among its tips for night shifts. For employers, it calls bright light in shift schedules a complicated area that is still relatively untried, and it advises getting specialist advice first (HSE, 2006).

How bright is 5,000 lux? Light levels indoors and outdoors.

Should you wear sunglasses after a night shift?

Several studies used them. In Eastman’s 1994 study, the body clock shifted later only in people who wore goggles. The authors think daylight on the way home after a night shift holds that shift back (Eastman et al., 1994). Boivin and James used tinted goggles that let through 15% of visible light, and Smith and colleagues had people wear dark sunglasses whenever they were outside (Boivin & James, 2002; Smith et al., 2009).

These were study plans tested with a few dozen people, not a rule for your commute.

How do you sleep after a night shift?

Day sleep is usually lighter and shorter than night sleep, and warmth and daytime noise disturb it more often (HSE, 2006). The HSE’s tips for shift workers include darkening the bedroom with heavy curtains, blackout blinds or eye shades, and keeping to a sleep schedule once you have found one that suits you.

The light studies did the same: fixed sleep times in a dark room. In Boivin and James’s study, the nurses slept 8 hours in darkness, starting 2 hours after their shift ended (Boivin & James, 2002; Smith et al., 2009).

What about days off and rotating shifts?

A full switch to a night schedule would leave you out of step with everyone else on your days off. Smith and colleagues write that few night workers would want that. They aimed for a compromise: the clock moves partway, enough for day sleep after a shift and for late night sleep on days off (Smith et al., 2009).

For rotating rotas there is no single plan either. The HSE writes that there is no single shift system that suits everyone, given how different jobs and workplaces are (HSE, 2006).

Is morning light advice made for shift workers?

Mostly not. The expert recommendations by Brown and colleagues were written for healthy adults with regular daytime schedules. The authors call light advice for night shift workers “still not mature” and point out that their recommendations are not meant for that purpose (Brown et al., 2022). A 2026 policy brief lists guidance for shift workers among the open research priorities (Piper et al., 2026).

LightOtter is a morning light app. Its minutes are its own estimate from clouds and the height of the sun, made for a day schedule where the morning starts your day. After a night shift, the morning is when you go to bed, and the studies above tried to keep bright morning light out. So the estimate may not fit your nights. Never look directly at the sun.

How LightOtter estimates its morning minutes, and where that stops.

What this is not

This guide is about the timing of light, not about medicine. The studies are small, and no source we checked gives a light dose in lux or minutes for your rota. Lighting at work and the shift plan are matters for your employer and occupational health service: in the UK, the HSE says employers have legal duties to assess the risks of shift work (HSE, 2006). If tiredness or sleep problems last, talk to a doctor.