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Working Nights Could Increase Risk of Ovarian Cancer



In the U.S., roughly 20,000 women receive an ovarian cancer diagnosis each year. While ovarian cancer ranks as only the eighth most common form of cancer diagnosed in U.S. women, the disease has the highest death rate of any cancer of the reproductive system with over 14,000 deaths annually.

When evaluating risk factors for the disease, oncologists have long looked at age, weight, reproductive history, diet, and family history as potential warning signs of ovarian cancer. Now, according to the results of a new study, doctors may need to start adding one more factor to the list of potential risk factors- whether a patient works nights.

According to researchers at the Fred Hutchinson Cancer Researcher Center in Seattle, Washington, women who work shifts at night have an increased risk of developing ovarian cancer. Building off an earlier study that found a link between night shift workers and an increased risk of breast cancer, researchers have now discovered the risks of working at night also include ovarian cancer.

The findings of the study were published in the journal Occupational and Environmental Medicine.

An Increased Risk

Involving over 1,100 women with the most common type of advanced ovarian cancer and approximately 390 with an early stage of the disease, the study compared the medical and personal history of these women with a group of over 1,800 women who were not diagnosed with ovarian cancer.

Study participants between the ages of 35 to 74 were asked about the hours they work, including whether they have ever spent time working overnight.

Among the women with an advanced form of ovarian cancer, approximately one out of four had previously worked nights, while one out of every three women with early-stage cancer claimed to have worked night. Comparatively, only one out of five women in the group without cancer had ever worked nights.

In all three groups of participants, the average number of years spent working night was between 2.7 and 3.5. The careers of these women spanned a variety of industries, with the most common in the fields of food service, health care, office administration, and support.

From the available data, researchers concluded that working the night shift increased a woman’s chance of developing advanced cancer of the ovaries by 24 percent and increased the risk of developing early-stage cancer by 49 percent. Researchers also concluded that this increased risk was limited to women over the age of 50.

Morning Person or Night Owl

Researchers were also able to determine that a woman’s risk of developing ovarian cancer by working the night shift varied depending on their preferred sleep schedule.

Women who reported a preference for the early morning were at a slightly higher risk when compared to women who preferred being up late at night.

Explaining this difference, researchers hypothesized that women who enjoyed early mornings but were forced to work nights would be under greater stress and strain from having to work at a time outside of their comfort zone. While a woman’s risk was only slightly higher if she preferred mornings but worked at night, this provides just one more reason why a person should maintain a work schedule that fits their lifestyle.