Sleeping after night shifts

If you work nights, the pattern may be familiar. You get home exhausted, yet sleep is slow to come, or it comes and then ends around midday with nowhere near enough hours behind you. That comes down to when you're trying to sleep.

Sleeping while the clock says day

Two things decide how easily sleep comes. The first is sleep pressure, the drive to sleep that builds the longer you're awake and is cleared by sleeping; a chemical called adenosine, which builds up in the brain during waking hours, carries much of it. The second is the body clock, a small cluster of cells in the brain called the suprachiasmatic nucleus (the body's master clock), whose alerting signal rises through the biological day.

At night the two work together, high pressure meeting a low alerting signal. After a night shift they pull against each other. You go to bed with plenty of pressure, but as the first hours of sleep clear it, there's less left to hold off a clock now signalling morning, so sleep thins out and you wake early. The clock doesn't simply switch to nights either: light reaching the eyes is the main thing that sets it, and the journey home in daylight tells it the day has started.

What studies of night work found

Åkerstedt (2003) reviewed the research on shift work and sleep. After nights, the most troublesome short-term effects were difficulty getting to sleep, shortened sleep and sleepiness at work, continuing into the days off that followed. Reassuringly, he found no clear sign that long-term shift work leaves people with chronic sleep problems.

The drive home is where the risk lies. Lee and colleagues (2016) had 16 night-shift workers drive for two hours on a closed test track twice, once after a normal night's sleep and once straight after a night shift. After the night shift there were 11 near-crashes across 6 of the 16 drives, and 7 drives were stopped early for safety. After sleep there were none. It's a small study, but the drowsiness measures it reports, from longer blinks to drifting out of lane, were all worse after the shift.

Caffeine hits day sleep harder too. It works by blocking the receptors adenosine acts on, so the pressure is still there but less of it is felt. Carrier and colleagues (2007) gave 34 regular, moderate caffeine users 200 mg of caffeine or a dummy capsule, split between three hours and one hour before bed, in a double-blind crossover. Half slept at night; half stayed up all night and slept in the morning. Caffeine disturbed sleep in both groups, but in the daytime sleepers it cut sleep efficiency (the share of time in bed spent asleep) further, and only they lost total sleep and dreaming (REM) sleep. The authors' explanation fits the mechanism above: by stripping out some deep sleep, caffeine gives the clock's daytime wake signal more room.

Getting home and getting to sleep

If you feel sleepy at the end of a shift, don't drive. The Highway Code (rule 91) says driving tired greatly increases your risk of a collision and advises against starting a journey tired; if sleepiness comes on during the drive, stop somewhere safe, which doesn't include a motorway hard shoulder. Get a lift or use public transport on those mornings. If you're nodding off without meaning to on a regular basis, government guidance says you must not drive until you're free of it.

For caffeine, we ask you to keep it to the first half of the shift and to leave about eight hours between your last single coffee-sized drink and day sleep. Stronger drinks, a double shot or a large energy drink, belong at the start of the shift only. We set that line from studies like Carrier's; we found no guideline giving a tested cut-off for night workers, so treat it as a working rule.

Beyond that, the bedroom itself has to make day sleep possible. Blackout blinds or an eye mask keep light off the clock; earplugs or a steady background sound cover daytime noise; and the people you live with should know which hours are yours. These steps come from how the clock and sleep work rather than from trials in night workers; they make day sleep easier to start and hold without removing the underlying difficulty.

Your diary and the plan

Your diary records day sleep as well as night sleep, so we can see how long you get after each shift. The plan changes one or two things at a time and judges them on that record. If you're nodding off without meaning to, or sleep stays poor on your days off as well, see your GP.