Night work linked to increased rates of cancer

The Danish government has recently begun paying compensation to women who have developed breast cancer after long spells working nights following a ruling by the International Agency for Research on Cancer (IARC ), an arm of the UN's World Health Organisation.

Kathy Sinnott, MEP for Munster, said: “Working the overnight shift has been linked to an increased risk of developing cancer. Research has found that men who work the night shift have higher rates of prostate cancer, while women have higher rates of breast cancer.”

The World Health Organisation declared night work a probable carcinogen. The designation, also endorsed by the American Cancer Association, has put working at night into the company of UV radiation and anabolic steroids as risk factors for cancer.

Scientists now think there might be a real biological basis for the night shift - cancer link. Working the night shift is dangerous because it disrupts the circadian rhythm - the “clock” that tells the body when to sleep and when to wake, and regulates other important biological processes. The hormone melatonin, which is vital to the suppression of tumours, is produced at night. Light shuts down melatonin production, so being exposed to artificial light in the evening could mean a melatonin deficiency.

Added Mrs Sinnott, who is a member of MEPs Against Cancer: “The balance between day and night is very important to the body in other ways, eg, getting enough daylight, and many of those processes could also play a role in determining a person’s resistance to cancer. Further, not getting enough sleep, a common problem for night shift workers who often have other daytime responsibilities, weakens the immune system, making the body more vulnerable to an attack from cancer cells.”

Research carried out in the US found that women who regularly worked night shifts for up to three years were 40 per cent more likely to develop breast cancer than those who did not work at night. And the risk increased to 60 per cent for those who regularly worked nightshifts for more than three years. In a study published last year, Danish scientists found that women who had worked predominantly at night for at least six months in their working life were 50 per cent more likely to develop the disease.

Mrs Sinnott, a member of the Committee on Employment and Social Affairs, added: “It was previously thought that people who worked night shifts, adjusted to this routine. However, this is not the case. Research shows that night workers do not become night people but become very tired day people. A number of women who are victims of breast cancer are challenging in the UK courts. It is important that employers and employees should be conscious that there are risks associated with night work. This should be taken into consideration when developing rotas and particularly when employees have other additional risk factors for cancer. The lesson here is that no person should be kept on night work for extended periods of time.”

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