This story is from Surviving the Night Shift, an episode of Business Daily presented by Manuela Saragosa and produced by Sarah Stolarz. To listen to more Business Daily episodes from the BBC World Service, please click here.

Tracey Loscar, a paramedic from Alaska, is 16 hours into a 24-hour shift at work. She does four of these shifts a week and has worked nights for 17 years.

“We joke that by day one, you walk in ready to take on the world, and by day four you’re ready to burn it down,” she says.

You constantly have to override this sort of biological drive from the clock saying you should be asleep

“I like the rhythm of the night. There’s less people on the road, the variety of calls, the pattern is different, less commercial businesses are open,” says Tracey. But in her line of work it’s also potentially hazardous. “Night time is more dangerous on a variety of fronts,” she says. “If your reaction time or observation time is a little slower, it certainly increases our risk while we are working. It’s very daunting.”

Around the world, millions of people work nights. There are few official figures but according to a study by Princeton University, an estimated 7-15% of the workforce in industrialised countries were engaged in some form of night work, despite the World Health Organization having classified night work as a probable cause of cancer due to disruption of circadian rhythms.

So how did working all night start anyway?

“From (Thomas) Edison’s production of the first cheap commercial lightbulb, we were able to invade the night at low cost and sleep was the first victim,” says Russell Foster, a sleep expert and Oxford University professor. “The key problem is we have this internal biological clock which is set to the external world as a result of exposure of the light/dark cycle.”

He says night workers are exposed to low light levels during the overnight shift, but as they encounter bright natural light on the journey home, their internal clocks lock on to the normal light-dark pattern that day shift workers are on. “So, you constantly have to override this sort of biological drive from the clock saying you should be asleep.” And it doesn’t matter if you are working night shifts on a regular basis either, he adds, unless you can hide yourself away from the light completely once you have finished your shift and the day creeps in.

We’re not going to put the 24/7 genie back in its bottle - Professor Russell Foster

So, what sort of physical effects does night shift work have on your body? Foster explains that overriding this biological clock makes you activate your “stress axis”, which is how your body reacts in a fight-or-flight situation. “We’re squirting out glucose into the circulation, we’re increasing blood pressure, we’re driving up alertness to deal with potential threat and of course we’re not, we’re just working,” says Foster.

He warns that sustained levels of stress can lead to cardiovascular disease, or metabolic abnormalities such as type 2 diabetes. Stress can also supress the immune system, which may be the basis of higher rates of colo-rectal cancer and breast cancer.

Those are the long-term effects, but of course being sleep deprived affects you in the short term as well. The most obvious effect being tiredness. Failure to take in information correctly, failure to pick up on social signals and a loss of empathy are all symptoms.

There is research to suggest that carbohydrate consumption can go up by 35-40% after only four or five days of restricted sleep due to the increased level of hormone being released called ghrelin that makes us hungry

“We’re not going to put the 24/7 genie back in its bottle,” says Foster, but he warns that companies whose employees do night shift work could be setting themselves up for lawsuits in the future if they don’t demonstrate they are taking all reasonable measures to try and mitigate some of the problems associated with working at night.

As well as instituting more regular health checks for workers, he says that “a really low-hanging fruit would be (providing) the appropriate nutrition. Knowing that you’re at risk of cardiovascular disease and metabolic problems, such as diabetes. Then the appropriate sorts of nutrition should be made available to night shift workers.”

As anyone who has worked through the dead of night knows, it’s not easy to get your hands on healthy food. And interestingly, there is research to suggest that carbohydrate consumption can go up by 35-40% after only four or five days of restricted sleep due to the increased level of a hormone being released called ghrelin. It makes us hungry and encourages us to reach for sugar and carbohydrates. “Ultimately this is not great for obesity or conditions such as type 2 diabetes,” points out Foster.

All that sleep deprivation carries not just a health cost but an economic one too, according to Marco Hafner, a senior economist at the research institution Rand Europe. “In the UK, we find that a lack of sleep costs the economy up to £40bn a year," he says, "which is roughly 1.8% of the UK GDP – that’s a mix of lost productivity and mortality effects.”

Are governments actually taking any notice in terms of making public policy? Marco Hafner says it’s at the early stages but “we know that the Centers for Disease Control and Prevention (in the US) has looked at this and has actually proclaimed insufficient sleep a public health epidemic, so there’s increasing awareness of lack of sleep being a public health problem.”

So why do it then? When there is so much evidence about the health risks of working the night shift, why would you put yourself through it? Well, many people don’t have a choice, and paramedic Tracey Loscar points out it does have its perks. “The schedule we have right now works quite well for my family… I get two weeks off every month. I work a long week but then I have seven consecutive days off and that’s seven consecutive days with my children and to make plans.”

“I knew what I was getting into,” she continues. “I’m very cognisant of my sleep schedule, I’m very cognisant of my physical activity and what you’re eating and I will cancel things in lieu of recovery time to make sure I try and mitigate it as much as I possible.”

She explains that night shift working can suit certain personality types: “I would say the kind of person that prefers or exclusively does night shifts is someone who is a little more introverted by nature.” She adds, “there’s less exposure to the public so you tend to find the people that prefer nights are the people who prefer to be left alone to do their job.”

But has doing 17 long years of night shifts not had any effect on her physical or mental health? “Well I sure spent a lot of it tired!” she laughs.

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