It’s not just emergency workers who endure perma-lag (Image: Ken Schles/Gallery Stock)
Read more: “The night: The nocturnal journey of body and mind“
SOMETIMES, there just aren’t enough hours in the day. Most of us have pulled an all-nighter at one time or another. There are even those who make a habit of it: Thomas Edison reputedly worked without sleep for days on end when in the throes of invention, as did his arch-rival, Nikola Tesla.
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But for most of us, pushing on past bedtime takes real effort. Our body’s master clock – a collection of about 50,000 neurons in the brain’s suprachiasmatic nucleus – responds to external cues, such as light, and coordinates the cellular clocks in our organs and muscles. It influences the rhythms of our autonomic system and spurs our endocrine system to secrete hormones associated with everything from sleepiness to stress – and it is extremely hard to ignore. “That’s why shift workers find it difficult to get enough sleep – during the day, the biological clock is promoting wakefulness,” says Christopher Morris, a researcher in sleep medicine at Harvard Medical School. Imagine jet lag as a way of life and you get the idea.
It is not just security guards and emergency workers who have to endure this perma-lag. One in five US employees , and 1 in 15 works late shifts exclusively. Many people involved in global markets log on outside normal office hours. And yet more simply keep beavering away long after the sun goes down: gruelling hours are a point of pride in some professions. That might be good for the economy, but it’s not good for our health. Some sleep researchers fear that we are heading for an epidemic not just of fatigue, but of killer diseases.
“It is not just emergency workers who have to endure perma-jet lag”
has an unusual background for someone who studies sleep. He served as a police officer in South Central Los Angeles. There he learned first-hand about the toll consecutive night shifts can take – sometimes leaving him unsteady at the wheel of his car or short-tempered when dealing with suspects. “It wasn’t the kind of cop I wanted to be,” he says. Now at the Sleep and Performance Research Center at Washington State University in Spokane, he is looking into the physiological consequences of shift work.
Vila and his colleagues have explored many of the immediate hazards that are aggravated by fatigue. Cops who work at night are more likely to be injured, for example. But there may be longer-term risks, too: – a precursor for diabetes and heart disease – than those who rarely work nights.
Such effects are also seen in the wider world. An concluded that shift work is associated with a heightened risk of stroke and heart attack, and that this is most pronounced for people working nights (vol 345, p e4800). What’s more, studies hinting that it increases the risk of developing some cancers led the World Health Organization to declare in 2007 .
Why should this be? The answer might lie in a disconnect between two systems whose synchronicity is thought to control our sleep patterns. The homeostatic system is governed by how much sleep we have had: the neurotransmitter adenosine accumulates in the brain as long as we are awake. Too much makes us sleepy. The circadian system, on the other hand, is governed by external cues called zeitgebers, from the German for “time-givers”. Chief among these cues is daylight; we feel sleepy when it gets dark, thanks to the hormone melatonin. Failing to sleep at the “right” time throws the two systems out of sync, which can weaken the immune system and increase the risk of cardiovascular disease and type 2 diabetes.
It can be difficult if not (there is some evidence, for example, that people when they are sleep-deprived).
That said, there are ways to acclimatise the body to late shifts. Some long-term shift workers tinker with their sleep patterns by using prescription drugs such as modafinil to increase their alertness at night; others take melatonin to help them nod off during the day.
But most people don’t want to simply live for the night: it’s impractical and often hard to square with family life. Perhaps it would be more realistic to redesign work schedules. Vila points to the Calgary Police Service in Alberta, Canada, which ran a trial aimed at ensuring that enough officers were on duty during peak crime hours, while minimising the circadian disruption they had to endure. The result was a schedule that limited officers to two consecutive night shifts per week, and also allowed for occasional recovery weeks of purely daytime or afternoon work.
But such interventions are rare. Matthew Walker, director of the Sleep and Neuroimaging Lab at the University of California, Berkeley, says he is reminded of attitudes to smoking in the 1950s: researchers were sure it posed serious health risks, but the public were largely oblivious. “I really do believe it is of that same magnitude,” he says.
And if you’re still tempted to pull that all-nighter, think on this. For every Edison, there’s another visionary who more literally dreamed up their big idea: consider August Kekulé’s sleepy vision of the benzene molecule as a serpent swallowing its own tail. Walker’s research shows that skipping a night’s sleep makes people more likely to make rash decisions. So what you produce as you burn the midnight oil is unlikely to be your best work. As he says: “There is a very simple reason nobody ever tells you to stay awake on a problem.”
This article appeared in print under the headline “Graveyard shift”
