Linking Night Shift Work to Cancer Risk

A recent study found that women who work the night shift may have an increased risk of breast, skin, and gastrointestinal cancers.

Rapid globalization of the economy has spurred an increase in the number of shift workers. Data from the Centers of Disease Control and Prevention estimate that almost 15 million Americans work irregular schedules.   

Does working the night shift have an effect on our cancer risk?

A study recently published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association of Cancer Research (AACR), found that long-term night shift work among women increased the risk of cancer by 19 percent.

Most previous research has focused on the increased risk of breast cancer among female night shift workers, but the results have been mixed. This study analyzed data from nearly 4 million women and looked at the association between long-term night shift work and risk of nearly a dozen types of cancer.

"By systematically integrating a multitude of previous data, we found that night shift work was positively associated with several common cancers in women," said Xuelei Ma, PhD, oncologist at State Key Laboratory of Biotherapy and Cancer Center, West China Medical Center of Sichuan University, Chengdu, China. “The results of this research suggest the need for health protection programs for long-term female night shift workers."

Looking at individual cancers, the study found that women who work the night shift had a 41 percent increased risk of skin cancer, a 32 percent increased risk of breast cancer, and an 18 percent increased risk of gastrointestinal cancer.

In addition, the researchers found that for every five years of night shift work, the risk for breast cancer increased by 3.3 percent.

The researchers looked specifically at the effect of night shift work on female nurses. Compared to their colleagues who did not perform night shift work, female nurses who worked the night shift had a 58 percent increased risk of breast cancer, 35 percent increased risk of gastrointestinal cancer, and a 28 percent increased risk of lung cancer.

While people choose to work nights for several reasons, including better pay and an opportunity to go back to school, female night shift workers should be aware of the increased cancer risk associated with their job, and have regular checkups.   

"Long-term night shift workers should have regular physical examinations and cancer screenings," urged Ma.

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