Approximately 8.7 million people in the UK work night shifts, but humans are not meant to be awake at night. “It goes against our natural circadian cycle,” says Steven Lockley, visiting professor at the Surrey Sleep Research Centre, University of Surrey. “We have a clock in the hypothalamus in the brain, and that clock has evolved to control many aspects of our physiology.” This includes metabolism and immune system, hormones, and heart, lung and brain function. “We’ve evolved to be awake in the daytime and asleep at night. When we do shift work, we’re going against what our natural rhythms want us to do.”
This is true not just for those who work in the dead of night, but for those who work early and evening shifts. It means, says Lockley, “you’re not sleeping at the right time. Night shifts are the worst example, but all of these [shift patterns] move away from the circadian desire to keep a stable sleep-wake cycle.”
The knock-on effects on systemic health are many: “We know that shift workers have a higher risk of heart disease, hypertension, obesity, diabetes, stroke, depression, anxiety and some types of cancer.” The World Health Organization has classified shift work as “probably carcinogenic”. Depression is more likely. Working nights can raise cortisol levels, and impair cognition and memory. “When you mess up the circadian clock, you mess up all the systems it controls. For example, shift workers were at a much higher risk of contracting Covid that led to hospitalisation than non-shift workers,” says Lockley. Shift workers are more likely to smoke, and more likely to have relationship breakdowns.
Many shift working jobs are essential, but lots are not. “So the first question for society is: should we have shift work?” says Lockley. Yes if it’s for the emergency services, and hospital and care work. It’s harder to justify for restaurants, supermarkets, 24-hour news and radio, many cleaning staff, online shopping warehouse pickers, and all the other conveniences of modern life.
In a survey of workers from five unions by Sian Moore, professor of work and employment at Anglia Ruskin University, some said that working nights fits in with their life, “but even then, when you talk to them about their sleep, it’s pretty appalling”. It’s a “constrained choice”, she says – it was part of their job description, or people would take night shifts for the extra money, and many did it for childcare reasons, including being able to make school runs.
So if shift work is probably here to stay, “it’s about what you can do to mitigate it”, says Russell Foster, director of the Sir Jules Thorn Sleep and Circadian Neuroscience Institute at the University of Oxford, and author of Life Time, about the human body clock. More frequent health checks for long-term night shift workers, especially focusing on type 2 diabetes and obesity, should be done, he says, to spot “issues before they become chronic”. Employers should provide this, but if they don’t, an individual would do well to “take that seriously, particularly in the areas of metabolic abnormalities, where the data is clear.”
Lockley suggests taking steps to avoid accidents when working nights. “We know that night shift workers have a higher risk of accidents and injuries [at work], and they have a higher risk of a crash, particularly on the drive home,” says Lockley. One study found that after four consecutive night shifts, the risk of workplace injuries was 36% higher. Medical errors are more common on night shifts, staffed by fatigued doctors and nurses, raising patient safety concerns; night-time healthcare workers are also more likely to suffer “needlestick” or sharps injuries than those working during the day.
These immediate dangers can be tackled by companies and institutions. In Australia, where Foster was a visiting professor, he was struck by how hospitals would provide taxis for people to get home, eliminating the need to drive home while trying to stay awake. People who are driving after a night shift should be provided with a device or app that monitors eye roll and head nodding (or signs of “microsleeps”), he says.
More thought should be given to rota patterns, says Lockley. “There are worse and better ways to design a shift rota.” Employees’ night shifts should be minimised, and the transition between day and night should be managed. “Going from day to evening to nights is better. Try to avoid quick returns, where someone does an evening shift tonight and the morning shift tomorrow.” When he did a study with a healthcare trust, applying those rules to resident doctor schedules, “we saw about a 30% fall in serious medical errors because we reorganised the shift patterns in a more circadian-friendly way”.
Lighting in the workplace is another key factor. Cooler, bluish light, “makes the brain think it’s daytime, essentially. Just looking at the lightbulbs in the workplace would be a good way to start to look at alertness on duty”. Lockley also says that while screening for sleep disorders can improve the health of all employees, it may have a greater impact for those working nights. “If you have an undiagnosed sleep disorder, then you’re not going to sleep as well, you’re not going to recover, and you’re going to be more sleepy at work.”
Your natural chronotype – whether you’re an owl or lark, feeling more alert in the evening or the morning – will affect how you deal with a night shift, but very few people, even the most owlish, can adapt to working nights. Foster says 97% of people can’t. One study showed that oil rig workers – who work under bright lights at night, then sleep in dark windowless rooms in the day – can adjust towards the end of a two-week stint of working nights, but very few people, points out Lockley, can or would want to “live in a completely nocturnal way. When you’ve got days off, holidays, gaps between shifts, you end up reverting back”.
Many employers are taking the harms of night shift working seriously (Lockley is working with St George’s hospital in London, which has been awarded a grant to develop a health programme for night shift workers). But there is a sense, says Moore, that many employers are failing to protect staff. “Some of the fatigue assessments that were done in the past aren’t being done properly. People would have physical checkups, which are often now just done by surveys. Occupational health [services], something that might have been in place before, is not there. I feel things have got worse.”
In any case, it usually falls to individuals to put measures in place to survive the night shift. It’s hard to give generic advice, says Lockley, because so much is dependent on the shift itself, preceding shifts, a person’s chronotype and other variables (he has developed an app, Timeshifter, for jet lag and shift work, in which someone can put this type of information in to get an individual programme, including helping you plan when to seek light and caffeine).
But there are some broad rules. Maintaining a healthy lifestyle is key, but eating well on a night shift when often the only food available is from takeaways or vending machines is notoriously difficult. There isn’t much evidence for taking supplements, except for vitamin D (shift workers don’t get as much sunlight). Exercise is vital. “There’s a study that [showed] that night shift workers who exercised and had a healthy lifestyle generally reduced their chances of developing type 2 diabetes,” says Foster – to only just above the average level of someone who doesn’t work night shifts.
One often-overlooked side-effect of night working is the impact on relationships and family life. In her survey into the effects of night shift working, Moore received reports of one parent finishing a shift and the other “literally handing over the child in a car park, on their way to work. That’s obviously very difficult”. Although shift working can reduce childcare costs, “at the same time, it’s having a big impact on the quality of relationships with children”. And with partners – one study found divorce and separation was six times more likely for men working night shifts in the first five years of marriage. Education, says Foster, is really important, “not only for the employee, so they can make a decision about whether the extra money is worth the health risks, but also for the people they share their lives with.”
While on a night shift, naps can help – if you’re able to take one – but timing is important. There are two processes driving sleep, says Foster – the circadian rhythm, and sleep pressure (the longer you’ve been awake, the greater the need for sleep). “A 20-minute nap will increase your performance and ability to function,” says Foster. The problem is that if you’re chronically tired – as many shift workers are – “you tend to drop very quickly into deep sleep, and waking from that can leave you groggy and actually be counterproductive. A 10-minute nap is perhaps all you go for.” Having a nap too close to the end of your shift could hold off the sleep pressure, detrimentally, but by then for most people, says Foster, “the sleep pressure is probably so high that getting off to sleep won’t be too much of an issue.” It’s probably safer, though, to take a short nap before work.
Caffeine could also make getting to sleep at the end of your shift harder. “The general advice tends to be to use it little and often,” says Lockley. By little, he means 0.3mg per kilo of body weight, so about 21mg an hour for a 70kg person. “That’s half a can of Coke, half a weak tea or coffee. It’s not very much, but that amount every hour, on average, is all the caffeine you need to stay alert, and minimise the effect on sleep.” Ideally, he recommends people “stop using caffeine about six hours before they plan to sleep”.
Sleeping pills are not advised, says Foster. “They sedate you, they don’t provide a biological mimic for sleep.” Many night shift workers become dependent on alcohol for the sedative effects, and the stimulant of cigarettes. Melatonin is sometimes prescribed for sleep problems and jet lag symptoms, but Foster says it’s often misunderstood. “It is not a ‘sleep hormone’, it is a biological marker of the ‘dark’ and a very mild modulator of sleep. In the study showing the greatest efficacy, it reduced the time it took to get to sleep by 20 minutes, but that doesn’t happen with everybody.” Foster also points out that one recent study suggested people with long-term use of melatonin were at higher risk of heart failure. “That’s the first real evidence that melatonin is bad for you.”
In the past, wearing dark glasses on the way home in daylight, was thought to aid subsequent sleep, but Lockley points out increasing sleepiness en route is dangerous (most accidents happen close to home). “That light is keeping you awake and keeping you alive,” he says – whether you’re driving, or crossing the road.
Coming off a night shift, the usual sleep hygiene advice remains – create a calm and dark sleep environment, and have a wind-down period. Turn your phone off, and make sure friends and family know not to disturb you. Earplugs will probably help to block out the daytime noises. Don’t be tempted to do a few jobs around the house when you get home. “The longer you wait after a night shift,” says Lockley, “the harder it is to fall asleep, and the shorter you’ll sleep.” Of course, then it might be time to do it all over again. It’s a small consolation, but with the days getting longer again, the life of night shift workers won’t be led almost entirely in the dark.