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).
