Shift Work May Fuel Aggressive Breast Cancer Growth

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A new study from Texas A&M University suggests that disruptions to the body's internal clock caused by shift work may increase the development and spread of aggressive breast cancer. Researchers found that mice with genetically engineered breast cancer that lived on a disrupted light cycle developed tumors around 4 weeks earlier and exhibited more aggressive, fast-spreading cancer compared to mice on a standard day-night schedule.

Why it matters

The findings raise concerns about the health impacts of shift work, which is common in industries like healthcare, transportation, and manufacturing. Disruptions to the body's circadian rhythms have been linked to increased cancer risk, and this study indicates the effects may be particularly pronounced for aggressive breast cancer.

The details

In the study, researchers divided mice engineered to develop breast cancer into two groups - one on a standard day-night cycle, and one with a disrupted light schedule to compromise their internal clocks. The circadian-disrupted group developed tumors around the 18th week, about 4 weeks earlier than the control group. The disrupted mice also exhibited more aggressive, fast-spreading tumors and compromised immune systems that accelerated cancer growth.

• The study was published in the journal Oncogene in January 2026.

What they’re saying

What’s next

The research team plans to further investigate how the effects of chronic circadian disruptions might be reversed in humans, with the goal of improving health outcomes for night shift workers and others with irregular sleep schedules.