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Last Updated: Wednesday, 5 December 2007, 00:06 GMT
Can our bodies adapt to being night owls?
Working shifts including at night is common in the medical profession

By Clare Davidson
Business reporter, BBC News

How does it feel to be working while most people are sleeping? Following a series on night work, we look at the side effects of working unusual hours.

At only 27, Abigail Medniuk is resigned to decades of working odd hours.

"I knew my career would be open to a lifetime of night shifts and anti-social hours," says Dr Medniuk, a senior house officer in anaesthetics at Kent and Sussex Hospital.

Man sleeping
Night workers are always fighting the natural light which the body finds hard to adjust to
James Waterhouse, Liverpool John Moores University
Since qualifying in 2004, her hours have varied considerably, she says as she rushes between patients. At one extreme she has worked continuously on nights over seven days.

In her new job she avoids the long stretches of nights, but jumps between night shifts and day shifts at two or three day intervals.

She accepts the hours, but is emphatic on one point: "You never get used to it."

Body clock

What becomes immediately obvious from talking to researchers is how disruptive night work is for the body. This has huge health implications.

The most obvious result of night work or shift work outside normal office hours is the disruption to the circadian rhythm, or body clock.

The body clock helps us stay awake and alert in the daytime and enables us to sleep and recuperate at night, explains Professor James Waterhouse, a sport and exercise science specialist at Liverpool John Moores University.

Our body temperature rises during the day and boosts naturally occurring levels of adrenaline. In the evenings, the body cools down, reaching its lowest temperature in the early hours.

"Night workers are always fighting the natural light, which the body finds hard to adjust to," he says.

Doing damage

It is not simply a matter of inadequate sleep. Even when workers do sleep it is often poor quality and interrupted.

Exxon Valdez oil slick
Fatigue has been cited as a factor in major accidents
"Workers can take the phone off the hook and have the thickest curtains possible, but surrounding daytime noises continue regardless," says Professor Jim Horne, director of Loughborough University's Sleep Research Centre.

Fatigue and accumulative sleep deprivation can be insidious, developing slowly over time with workers unaware of its impact, according to the Health & Safety Executive (HSE).

But it can also be potentially disastrous, if judgement is impaired or concentration compromised, especially for operators of machinery. According to the HSE, the incident of accidents on night shifts are higher.

Night-time workers' fatigue has been cited as a factor in several well-known disasters, according to a report by the Association of Professional Sleep Societies. These include the Exxon Valdez oil spill, the Bhopal chemical blast and the Chernobyl nuclear explosion.

Cutting the risks associated with night and shift work would help improve workers' health and safety. But the HSE is keen to stress that it could also help businesses financially by reducing absenteeism, injuries and accidents, while also boosting productivity.

24 hour society?

Accidents aside, researchers say disrupting the circadian rhythm and the resulting lack of sleep can have a range of other effects.

Research has shown gastrointestinal disorders are common complaints by night workers, says Debra Skene, head of the Neuroendocrinology School of Biomedical and Molecular Sciences at Surrey University. These include indigestion, loss of appetite and peptic ulcers.

In a sense 24-hour society is here but it isn't here truly
James Waterhouse, Liverpool John Moores University

And increased risks of cardiovascular problems, such as hypertension, are another issue. What causes this is not exactly clear, says Professor Waterhouse.

But antisocial hours means not only are workers awake when their bodies want to be asleep, they tend to have less access to facilities that help maintain a healthy lifestyle. For example night workers are less likely to join a gym or association that might have physical and social benefits, he says.

"In a sense the 24-hour society is here, but it isn't here truly."

Access to decent healthy food at night is a common problem. He says often night workers eat their evening meal with their families or partners because it is the main time to catch up. But this can create problems regarding what to do during the main break at work.

"People don't feel like a full meal so resort to eating crisps or chocolate," he adds.

'No solution'

There are better and worse aspects of the different types of rotas used for night work, says Dr Medniuk.

It is a relief that in her new job she doesn't face the prospect of seven consecutive nights at work. On the other hand, her current rota is completely irregular and she says the time off is not enough to do much.

Night work
Night workers are those who regularly work for at least three hours between 11:00pm and 6:00am
Employers must offer a free health assessment before starting work at night and regularly after that
Fatigue, sleep deficit and a disrupted circadian rhythm are said to be exacerbated by 12 hour shifts
Advancing shifts (mornings, then afternoons, then nights) are easier to adapt to than the reverse
Source: London Hazards Centre, Health & Safety Executive

These two models - one with the week of nights compared to two and three days stints - are commonly used by employers that operate shift or night work.

A more extreme option involves around a month of nights or late shifts followed by time off.

But fundamentally, the problem with all these patterns is the clash between trying to work at night, when everyone else including family and friends are not, while having a "normal" life in between researchers say.

"There is no solution because we tend to revert to being daytime creatures," says Professor Waterhouse.

He adds the best way to truly adapt to night work would be to stick to being awake at night even on days off. A weekend lie-in is not the solution, he says. Above all, the body wants regularity.

This applies not only to night shifts but also for people working other irregular shifts, says Professor Skene. Getting up at 4am or 5am is likely to mean people are always short of sleep because they are unlikely to have gone to bed the extra two to three hours earlier.

Moreover, constantly changing patterns is disastrous for the body as the circadian rhythm is "completely shot", says Professor Skene. It might take several weeks to rectify an irregular pattern over several years.

Night sky
The inbuilt body clock helps us sleep and recuperate at night
"What long term damage is done to other parts of the body - we have no idea," she adds.


A spokesperson for the Transport and General Workers Union says there is plenty of information available but all too often organisations don't seek advice when devising shifts.

Professor Horne echoes this, saying firms plan night shifts as if they were day shifts.

Working at night is "fundamentally different" and many decisions about shift patterns "seem haphazard" he says. This includes the increasing trend of 12-hour night shifts "even though there isn't the research to show it is a good idea".

Organisations can gain advice to avoid the worst case scenarios, he adds.

"Employers don't understand that working at night might be a health issue as well as a safety issue," says T&G.

Professor Waterhouse sums up the problem by saying society has fundamentally changed in a very short period, but human biology has not.

Some cope better than others, but whatever expectation we have of a 24-hour society, we cannot eliminate our inbuilt body clock.

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