Nightshift Work Promotes Ovarian Cancer

Researchers at the Fred Hutchinson Cancer Research Center (Seattle, WA, USA) conducted a study involving 1,101 women with invasive epithelial ovarian cancer, 389 women with borderline epithelial ovarian tumors, and 1,832 controls to evaluate the association between self-reported nightshift work—a known circadian rhythm disruptor--and ovarian cancer. For cancer cases, information was obtained as to tumor grade and morphology. Socioeconomic data, medical, occupational, and reproductive history, lifestyle, and activity preference (morning or evening) were collected from all participants.

The results showed that working the nightshift was associated with an increased risk of invasive and borderline tumors; however, little evidence was shown that the risks increased with increasing cumulative duration of nightshift work, and risks were not elevated in the highest duration category (over 7 nightshift work-years). Increased risks were restricted to women who were 50 years of age and older, and to serous and mucinous histologies of invasive and borderline tumors. There was suggestive evidence of a decreased risk of ovarian cancer among women reporting a preference for activity during evenings rather than mornings. The study was published early online on January 23, 2013, in Occupational and Environmental Medicine.

“We found evidence suggesting an association between shift work and ovarian cancer; the increased risks that we observed are consistent in magnitude with those observed for breast cancer in previous studies,” concluded lead author Parveen Bhatti, PhD, and colleagues. “This observation should be followed up in future studies incorporating detailed assessments of diurnal preference (i.e., chronotype) in addition to detailed data on shift schedules, and particularly whether circadian gene variants play a role in susceptibility to cancer in shift workers.”

Circadian rhythm is a biological process widely observed in plants, animals, fungi, and cyanobacteria. Health problems can result from a disturbance to the circadian rhythm, including seasonal affective disorder (SAD), delayed sleep phase syndrome (DSPS) and other circadian rhythm disorders. Shift work or chronic jet-lag have profound consequences on circadian and metabolic events in the body by favoring irregular eating times, altered insulin sensitivity, and higher body mass index (BMI). Shift-work also leads to increased metabolic risks for cardiometabolic syndrome, hypertension, and inflammation.

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Fred Hutchinson Cancer Research Center