Night Shifts may up Ovarian Cancer Risk in Women

Night shifts increase ovarian cancer risk in women, says a new study. The risk is higher for women who are early risers, the morning types or "larks" when compared to women who tend to sleep late called "owls".

The study was based on a study group of more than 1,000 women who were diagnosed with the most common type of ovarian cancer. The study also included 389 in primary stages of the cancer and 1,832 women without ovarian cancer.

The women in the study were asked about their lifestyles and their working hours. The International Agency for Research on Cancer has classified shift work as a risk factor for cancer as it disrupts the body's internal clock. However, previous research conducted on shift work and risk of breast cancer has yielded mixed results.

In the present study, one in four women with invasive ovarian cancer had worked night shifts compared to one in three women that had borderline disease. About one in five women in the control group (those without the cancer) had worked night shifts.

Both motherhood and being on the pill are known to lower ovarian cancer risks. In the study, women with ovarian cancer were less likely to be on the pill or have many children.

Data analysis showed that night shifts alone increased the risk of invasive ovarian cancer by 24 percent and borderline disease risk by 49 percent. Women who were over 50 years of age and worked late-night shifts were at an even higher risk of developing the cancer.

The risk of the cancer lowered in women who were owls or late-workers than in women who were the morning type or larks. Researchers add that this difference between "owls" and "larks" ovarian cancer risk was very small.

Centers for Disease Control and Prevention says that each year about 20,000 women in the U.S. get ovarian cancer. It is the eighth most common cancer in the U.S. Ovarian cancer usually occurs in women over 40 years of age. Treatment is most effective if the cancer is detected earlier, says CDC.

The study is published in the journal Occupational and Environmental Medicine.