Years of graveyard shifts appear to raise the risk of breast cancer. (Photo: Reuters)

Night shifts raise the risk of breast cancer

Women whose shifts include the four hours from midnight to four in the morning for much of their working life have an elevated risk of breast cancer.

If you are a woman who works night shifts you might consider looking for another job if you can. Women who spend much of their careers working graveyard shifts run a higher risk of contracting breast cancer, according to a Swedish study.

The study joins a host of other research findings showing that working at night is not good for your health.  A Canadian study from 2013 has also found that long-term night shift work doubles the risk of breast cancer. 

Night work for shorter periods does not appear to pose such significantly increased risks.

Over 20 years

The high-risk group consists of women up to the age of 60 who have worked night shifts for 20 years or more. The study was carried out by Professor Torbjørn Åkerstedt of the Karolinska Institute.

The study ran for several years.

The researchers based their findings on the 13,000 women in the Swedish Twin Registry and checked out how many worked at night. 

They charted the cases of breast cancer from the country’s cancer registry and made adjustments for a number of known variables that might bias results.

75 percent increase

Initially, when the researchers compared night shift workers with all the others who developed breast cancer they saw no clear differences. But when they singled out the women who had worked night shifts for decades they saw the spike in breast cancer risks.

The risk of breast cancer among women on night shifts for long periods was 75 percent higher than the normal risk. 

While the risk of getting breast cancer is two percent for women who have normal working hours, it jumps to 3.5 percent for those whose career was mainly made up of night shifts.

Translated by: Glenn Ostling

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