Working in night shifts has no impact on breast cancer probability: study

Washington D.C.: A recent research has found that working in night shifts has little or no effect on a woman's breast cancer risk.

This comes despite a review in 2007 by the International Agency for Research on Cancer (IARC) classifying shift work disrupting the 'body clock' as a probable cause of cancer. The research by following 1.4 million women in ten studies and seeing if they developed breast cancer examined whether night shift work increased women's breast cancer risk.

Ruth Travis, the study's lead author, said: "We found that women who had worked night shifts, including long-term night shifts, were not more likely to develop breast cancer, either in the three new UK studies or when we combined results from all 10 studies that had published relevant data."

The researchers found that the breast cancer cases were essentially the same whether someone did no night shift work at all or did night shift work for several decades, the combined relative risks taking all 10 studies together were 0.99 for any night shift work, 1.01 for 20 or more years of night shift work, and 1.00 for 30 or more years night shift work.

On an average one in seven (14 percent) women in the UK have worked in night shifts and one in 50 (two percent) have worked during nights for 20 or more years. Each year in the UK around 53,300 women are diagnosed with breast cancer and around 11,500 die from the disease.

Andrew Curran, an expert in the field, said: "Breast cancer is the most common cancer in women so it was vital for us to fund work in this area to establish if there is a link to night work."

He added, "In Great Britain, there are 2 million women, about one in six female workers, who are currently working in some types of shift work, and over half million of them are working in shifts that involves night work."

Curran further said this study has shown that night shift work, including long-term shift work, has little or no effect on breast cancer incidence in women. "However, there are a number of other known risks with shift work that employers must take into consideration when protecting their workers' health and safety," he added.

The research was published in the Journal of the National Cancer Institute.