Shift work and sleep

Roughly one worker in six in the UK works outside ordinary daytime hours, and a substantial proportion of them sleep badly as a direct result. The usual way of describing the problem — that shift workers do not get enough sleep — is only half of it, and the half that matters less.

The real difficulty is that the body's internal clock does not move when the rota does.

Why the clock does not simply adjust

Nearly every system in the body runs on a daily cycle: body temperature, alertness, digestion, hormone release, blood pressure. That cycle is governed by a clock in the brain, and the clock is set chiefly by light reaching the eyes.

Light is why a night worker rarely adapts. Driving home in the morning sun, doing the shopping in daylight, a weekend spent on an ordinary schedule — each of those resets the clock towards day waking, however consistently the nights are worked. The result for most permanent night workers is not a shifted clock but a clock permanently in disagreement with their life: trying to sleep when the body is signalling for alertness, and working when it is signalling for sleep.

The consequences are the familiar ones — difficulty getting to sleep after a shift, short and broken daytime sleep, waking unrefreshed, and sleepiness at work — and when they are persistent and tied to the work pattern, they amount to a recognised condition, shift work sleep disorder, rather than ordinary insomnia. The distinction matters because the treatments differ: the behavioural treatment for insomnia is not the right approach for a problem whose cause is a timetable.

The journey home is the dangerous part

This deserves saying before anything else, because it is where shift work actually hurts people.

Alertness bottoms out in the early hours, and a night worker driving home at the end of a shift is doing so at close to their worst. Severe sleepiness impairs driving comparably to alcohol, and does so without the driver being aware of how impaired they are — microsleeps of a few seconds happen without any memory of them. Collisions on the commute home from a night shift are a well-documented pattern, and the drivers involved almost always report having felt able to make the journey.

What helps, in rough order of usefulness: not driving at all after a night shift, which means public transport, a lift, or sleeping somewhere at work if that can be arranged; a short nap before setting off; caffeine before the journey, which buys perhaps half an hour; and stopping immediately at the first sign of drowsiness rather than pushing on for the last few miles. Opening a window and turning up the radio do nothing.

Anyone whose daytime sleepiness has persisted for three months or more, from any cause, is required to tell the DVLA — a rule that applies to sleep problems generally and not only to sleep apnoea.

The health picture, stated plainly

Long-term shift work is associated with a number of conditions, and the honest summary is that the associations are consistent but mostly modest, and that most of them are not inevitable.

The better-established ones are cardiovascular: raised blood pressure and an increased risk of heart disease and stroke. Then metabolic — weight gain and type 2 diabetes, which is partly about circadian disruption and partly about what is available to eat at three in the morning. Gastrointestinal trouble, including reflux and ulcers, is common enough to have been recognised for decades. Depression and anxiety are more frequent among shift workers, as is problem drinking. And shift work puts strain on family life and friendships in ways that are hard to measure and that people consistently report as the worst part.

Night shift work is classified by the International Agency for Research on Cancer as probably carcinogenic to humans, on the basis of limited evidence in people and stronger evidence in animals. That classification is worth knowing about and worth keeping in proportion: it describes a possible increase in risk across a population over decades of night work, not a verdict on an individual career. It is one of several reasons the UK gives night workers a legal right to health monitoring.

What actually helps

Sleep as soon as possible after a night shift, rather than staying up and trying to sleep in the afternoon. Sleep taken immediately is longer and better consolidated, because it is still riding the tail of the night's sleep pressure.

Darkness is not optional. Blackout blinds or lined curtains, a sleep mask, and a dark room are worth more than any other single measure, because daylight reaching the eyes both prevents sleep and resets the clock in the wrong direction.

Dark glasses on the way home. Wearing sunglasses for the journey after a night shift reduces the morning light signal and makes the sleep that follows easier. It looks eccentric and it works.

Quiet, and a household that understands. A note on the door, a silenced phone, and an agreement with whoever else lives there about the hours that are off limits. Earplugs or a steady background sound where the street is noisy.

Split the sleep where one block is not possible. A long sleep after the shift plus a nap before the next one is a legitimate strategy, not a failure to sleep properly, and it suits a good many people better than attempting seven or eight hours in one go.

Nap before the shift and, where the employer allows it, during it. A nap of twenty to thirty minutes measurably improves alertness and reaction time. Longer naps risk grogginess on waking, which takes fifteen or twenty minutes to clear — a consideration for anyone who may be called on immediately. Controlled napping on night shifts is standard practice in aviation and increasingly in healthcare, and asking about it is reasonable rather than presumptuous.

Bright light at work, dim light before sleep. A well-lit workplace helps alertness during the night, and keeping the last hour before bed dim helps the transition into sleep.

Caffeine, used deliberately. It works, and it works best taken early in the shift rather than steadily through it, and not within several hours of the intended sleep. Its half-life is long enough that a drink at five in the morning is still active at lunchtime.

Eat as though the shift were a day. A proper meal before the shift, something light during it, and not a heavy meal in the small hours, when digestion is at its slowest. Reflux is one of the commonest complaints among night workers and is largely a timing problem.

On the rota itself, two patterns are better than their alternatives. Rotating forwards — mornings, then afternoons, then nights — is easier to adapt to than rotating backwards, because stretching a day is easier than shortening it. And two or three night shifts in a row, followed by proper time off, is generally better tolerated than longer runs. Where there is any say in the pattern, those are the things worth asking for.

Exercise and daylight on days off both help, with the qualification that bright light at the wrong time of day works against a night worker rather than for them.

Two things that are not available here

Melatonin is sometimes suggested for shift workers, and in the UK it is a prescription-only medicine. It is not sold in health food shops here, whatever advice written elsewhere assumes, and products ordered from abroad are unregulated and of unknown content.

Modafinil is licensed in some countries for shift work sleep disorder. It is not licensed for it in the UK: a European review concluded in 2011 that the evidence did not justify its use outside narcolepsy, and the other indications were removed. It is not a treatment to expect or to ask for.

What the law provides

This is the part of the subject most often left out, and it is the part a shift worker can act on.

Under the Working Time Regulations, a night worker is broadly someone who regularly works at least three hours during the night period, which is 11pm to 6am unless another seven-hour period including midnight to 5am has been agreed. Night workers:

• Must be offered a free health assessment before starting night work and at regular intervals afterwards. This is a right, it is at the employer's expense, and a great many people entitled to it have never been offered one.
• Should not normally work more than an average of eight hours in each twenty-four.
• Are entitled to the general protections: an average working week of no more than forty-eight hours over a seventeen-week period, eleven hours' rest between shifts, a day off each week, and an uninterrupted twenty-minute break after six hours, away from the workstation and not at the start or end of the shift.

Some sectors are partly exempt, including emergency services and much of transport. Opting out of the forty-eight-hour average is possible, must be in writing, and must be voluntary.

Occupational health guidance also identifies people for whom night work warrants a careful assessment or should be avoided: anyone with diabetes, a heart or circulatory condition, a stomach or bowel disorder, a condition that worsens at night, or a condition needing medication on a strict timetable; workers under eighteen; pregnant workers; and anyone whose night vision is poor, where the job involves driving. Age and the menopause are both recognised as grounds for review rather than for exclusion.

When to see a GP

• Sleepiness that persists through days off, which suggests something beyond the rota — sleep apnoea in particular, which shift work both masks and worsens.
• Falling asleep at the wheel, or any near miss on the journey home. This is urgent rather than something to mention at the next appointment.
• Low mood, anxiety, or drinking to get to sleep.
• Persistent heartburn, indigestion or bowel trouble that tracks the shift pattern.
• Any long-term condition that is becoming harder to manage around the hours — the dose timing of a medicine often needs changing rather than the medicine.
• Before relying on anything bought over the counter to sleep after a shift, which is where a short-term fix most often becomes a long-term problem.

It is also worth asking the employer for the night worker health assessment, which exists precisely to catch these things and costs nothing.