The Health Risks of Shift Work

More than four million people in the UK do shift work. Some of this work is inevitable. Doctors and nurses, for example, work shifts in hospitals to keep patients secure and alive. Police officers and security guards do shifts to ensure the majority of citizens can sleep through the night without fear.

An increasing number of employers expect staff to work shifts for other reasons. They want to make the most of factory machinery to maximise efficiency and profits. Or they need staff to be available for issues that may crop up from business partners working in different time zones around the world. These shifts may well attract allowances that boost pay, but research has shown that shift work can carry health risks.

Circadian Rhythms

The concept of circadian rhythms lies behind much of this research. A circadian rhythm is a recurring and natural biological process based on a 24-hour cycle. When something disturbs this process, such as a change in working hours, the rhythm may become imbalanced. Scientists have suggested this imbalance may affect the body’s immune system.


In 1987, a study linked night shift work to increased rates of cancer. Researchers proposed that the cause could be a disruption to circadian rhythms.

In 2009, the Danish Government fully accepted the existence of such a link. It arranged compensation for women with breast cancer who had worked for years on night shifts. The Danes took this action following a report from the International Agency for Research on Cancer. The Agency, which is part of the World Health Organisation, made shift work a Category Two cancer risk. Along with diesel engine exhaust, anabolic steroids and ultraviolet radiation, the Agency regards night shifts as a possible human carcinogen.

Other studies have assessed the percentage risk for women of developing breast cancer if they work at night. The average increased risk is 48%. These studies are not conclusive. Cancer Research UK, for example, advises caution before drawing conclusions. It argues that there are many factors such as obesity and alcohol that may relate to night shift workers and cause an increased risk of cancer.

Heart Disease

Ischaemic heart disease occurs when the body has a reduced supply of blood through the heart. The main causes are smoking, age, diabetes, high blood pressure and high cholesterol levels. Shift work may also increase the incidence of the disease. A 1986 study on long-term shift workers found they were three times more likely to have ischaemic heart disease than counterparts who worked ordinary hours.

Headaches and Other Problems

Shift work can, in some instances, lead to headaches. A study published in 2005 in America made a connection between irregular work hours and cluster headaches. This type of headache is particularly unpleasant. It affects around one in a thousand people and appears with little warning. The sufferer is in severe pain for up to three hours or more.

Research from a study of 200 shift workers has also highlighted other potential health problems. Among these are stress, difficulty concentrating, and poor sexual performance. Such problems mainly occur in the short term.

Car Accidents

Lack of sleep causes car accidents, and shift work can be a contributory factor. Research conducted in 2000 showed that driver tiredness leads to 45,000 serious injuries or deaths on the road. This figure is as high as the number of alcohol-related accidents.


Humans are not naturally nocturnal. In normal circumstances, most people function better during the day rather than at night. But it is possible to adjust to working at night, and thereby help reduce problems of tiredness and ill health. The crucial factor, according to doctors, is to have sufficient sleep during any 24-hour period. It’s also important to have this sleep, and to wake, at about the same time every day or night. This establishes a routine to which the body can adapt.

Medical experts recommend eight hours sleep per 24-hour period. Individuals differ, of course, but the amount of sleep should fall somewhere between five to nine hours.

Staying Awake

Even with sufficient sleep, it can be hard to stay awake during a night shift. Tried and tested techniques can help, however.

  • Where possible, avoid stimulants such as coffee. A quick walk in the fresh air can be far more effective at refreshing the mind and body.
  • Take exercise before the shift starts. This increases oxygen flow to the brain and enlivens the nerves.
  • Don’t drink alcohol before starting a shift. Alcohol can make the body and mind tired rather than stimulated.
  • When at work, don’t become too warm. Ensure there’s plenty of ventilation and light. And either talk to colleagues or listen to music to help keep the brain active.

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