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Is There A Risk Of Breast Cancer During Night Shift Work?

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Breast Cancer is one of the common killings of cancers in women. Cancer cells are formed in the breast and nipple region. It is also one of the biggest causes of death among women. There are many things associated with breast cancer formation, like exposure to cancer-causing substances and family inheritance.

Out of all the causes, one would never guess working night shifts could be linked to breast cancer. However, a few studies suggest that working night shifts for a prolonged period of time could increase the risks of developing Breast Cancer In Women.

Usually, women working in the hospitality industry, aviation, and police have to work overnight. As per scientists, these women are more prone to breast cancer than other women with regular jobs.

In a report submitted by International Agency for Research Cancer (IARC), a subsidiary of the World Health Organization (WHO), work shifts contribute to cancer just like diet impacts on the risk of developing the disease. As the shifts can alter the sleeping pattern of a person, it increases the exposure of women to artificial light. This is the link between breast cancer and night shifts.

Night Work Breast Cancer Risk

On average, there is a 5-12 percent chance for a woman to develop breast cancer at any point in time in her life. If there is a co-relation established between working night shifts and breast cancer, the risks could increase from 12 percent to 14-15 percent. Though an insignificant increase, even the slightest probability of developing breast cancer is a serious concern for women.

The relation between night shift and breast cancer

As mentioned above, our sleep pattern has severe health implications on our body. For the people who work night shifts, they are not exposed to natural light as much as the body would need. We are energetic during the day and tired at night, which is a natural cycle.

When women start working night shifts, they alter the cycle. They need to use external stimulators like artificial light and caffeine to stay alert and awake all night. The body needs sleep, but the brain has to stay awake. The disruption in sleep cycle and overexposure to artificial light could increase the chances of developing cancer. Exposure to artificial light reduces the melatonin in the body. This melatonin is ideally responsible for reducing tumor growth. Once the vital substance goes missing, the chances of a tumor increase, which could also be cancerous. Also, night shifts increase stress, which in turn increases the number of glucocorticoids that help tumors to grow.

Risk Of Breast Cancer During Night Shift Work

The conclusion to this question is quite complicated. Researchers have studied the co-relation between night work breast cancer risk. Studies are held among women of different groups, and the results have been multiple. These studies have suggested that the risk of breast cancer during night-shift work increases by 5-10 percent.

A few results of the studies are mentioned below:

  • ‌One particular study found that a woman’s risk to develop breast cancer increases every 5 years of working in night shifts. The chances could increase by 2 to 3 percent.
  • ‌A study done by researchers at John Hopkins University suggests that the chances of developing breast cancer are 20% more for women who work in night shifts regularly than women who work at regular timings.
  • ‌Another study found that if women work for a shorter time period in night shifts, the risk of breast cancer during night shift increases by 1 percent.
  • ‌ The same study draws a comparison between women who work in night shifts for a longer period of time. For instance, the women who work in night shifts for more than 20 years, the night work increases breast cancer risk by 9 percent.

The University of Oxford angle

However, it is a study done by the University of Oxford that makes all the complications arise. As per this study was done in 2016, there is no link between night shifts and breast cancer risk, although medical experts and researchers find the study and its outcomes not apt enough.

What were the drawbacks of the study by Oxford?

A few experts have criticized the study done by the University of Oxford, which claims there is a risk of breast cancer during night shift work timings. ‌The study done by the University of Oxford covered only a few women for a span below 5 years. The previous studies followed women for as long as 20 years to come up with conclusive data. A shorter period of time is not enough to draw conclusions.


Breast cancer is a fatal disease, and any cause or contributor should not be taken lightly. If you work night shifts, reduce your turns and talk to your employer about this. There may or may not be a co-relation of working late nights with the formation of cancer cells. However, it is always good to be safe.

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