Does night work put women's health at risk?

June 19, 2012

Breast cancer is the number one cause of female mortality. It affects 100 out of 100,000 women per year in developed countries. Each year, more than 1.3 million new cases are diagnosed, 53,000 of these in France.

The risk factors of breast cancer are varied. They include , late first pregnancy, low parity or hormone therapy, but other causes of breast cancer such as way of life, environmental or professional causes have not yet been completely identified.

In 2010, based on experimental and epidemiological work, the International Agency for Research on Cancer (IARC) classified work that disturbed the circadian rhythm as being "probably carcinogenic". The circadian rhythm, that regulates the alternation between and sleep, controls numerous biological functions and is altered in people who work at night or who have disrupted working hours. Several hypotheses have been put forward to explain the observed links between night work and breast cancer: exposure to light during the night, that eliminates the nocturnal melatonin surge and its anti-carcinogenic effects, disturbed functioning of the biological that control cell proliferation, or that can weaken the immune system.

So the Inserm researchers examined the effect of night work on the health of women in a major population study carried out in France between 2005 and 2008. The careers of 3000 women were examined, including each period of night work. In total, over 11% of women had worked nights at some time during their career.

The risk of developing breast cancer was 30% higher in women who had worked nights compared to women who had never worked nights. This increased risk was particularly marked in women who had worked nights for over four years, or in women whose working rhythm was less than 3 nights per week, because this led to more frequent disturbances between night and day rhythms.

Finally, the link between night work and seemed to be more marked when we looked at women who had worked at night prior to a first pregnancy. An explanation for this result could be that the mammary cells, incompletely differentiated in women before their first pregnancy, are more vulnerable.

"Our work has corroborated the results of previous studies and poses the problem of taking night work into consideration in public health management, especially since the number of women working atypical hours is on the increase", states Pascal Guénel, the main author of this work.

Explore further: Night shift might boost women's breast cancer risk: study

More information: Night work and breast cancer: a population-based case-control study in France (the CECILE study) , International Journal of Cancer, onlinelibrary.wiley.com/doi/10 … 2/ijc.27669/abstract

Related Stories

Night shift might boost women's breast cancer risk: study

May 29, 2012
(HealthDay) -- Women who work the night shift more than twice a week might be increasing their risk for breast cancer, Danish researchers find.

Rotating night shift work linked to increased risk of Type 2 diabetes in women

December 6, 2011
Women who work a rotating (irregular) schedule that includes three or more night shifts per month, in addition to day and evening working hours in that month, may have an increased risk of developing type 2 diabetes when ...

Recommended for you

Scientists unlock structure of mTOR, a key cancer cell signaling protein

December 14, 2017
Researchers in the Sloan Kettering Institute have solved the structure of an important signaling molecule in cancer cells. They used a new technology called cryo-EM to visualize the structure in three dimensions. The detailed ...

Newest data links inflammation to chemo-brain

December 14, 2017
Inflammation in the blood plays a key role in "chemo-brain," according to a published pilot study that provides evidence for what scientists have long believed.

One in five young colon cancer patients have genetic link

December 13, 2017
As doctors grapple with increasing rates of colorectal cancers in young people, new research from the University of Michigan may offer some insight into how the disease developed and how to prevent further cancers. Researchers ...

New strategy for unleashing cancer-fighting power of p53 gene

December 13, 2017
Tumor protein p53 is one of the most critical determinants of the fate of cancer cells, as it can determine whether a cell lives or dies in response to stress. In a new study published today in the journal Nature Communications, ...

Researchers develop test that can diagnose two cancer types

December 12, 2017
A blood test using infrared spectroscopy can be used to diagnose two types of cancer, lymphoma and melanoma, according to a study led by Georgia State University.

Cancer-causing mutation suppresses immune system around tumours

December 12, 2017
Mutations in 'Ras' genes, which drive 25% of human cancers by causing tumour cells to grow, multiply and spread, can also protect cancer cells from the immune system, finds a new study from the Francis Crick Institute and ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.