Parveen Bhatti, Ph.D., from the Fred Hutchinson Cancer Research Center in Seattle, and colleagues examined the correlation between self-reported nightshift work and ovarian cancer in a population-based case-control study involving 1,101 women with invasive epithelial ovarian cancer, 389 women with borderline epithelial ovarian tumors, and 1,832 controls. In-person interviews were conducted to collect shift work data.

The researchers observed an increased risk of invasive and borderline tumors seen with working the nightshift (odds ratios, 1.24 and 1.48, respectively). There was little evidence that risk increased with increasing cumulative duration of nightshift work, and risks in the highest duration category were not elevated. The increased risks were observed only for women aged 50 years and older, and for invasive and borderline tumors with serous and mucinous histologies. For women reporting a preference for activity during evenings rather than mornings, there was suggestive evidence of a decreased risk of ovarian cancer.

"We found evidence suggesting an association between shift work and ovarian cancer," the authors write. "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."

Abstract
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