Working night shifts, traveling across time zones or keeping an irregular sleep schedule may increase the risk of aggressive breast cancer, according to new research from Texas A&M University. Scientists found that long-term disruption of the body’s internal clock changed breast tissue and weakened immune defenses, allowing cancer to develop earlier and spread more easily.
In the study, subjects exposed to irregular light and sleep patterns developed breast cancer weeks sooner than those on a regular schedule. Their tumors were also more aggressive and more likely to spread to the lungs. Researchers found that circadian disruption altered healthy breast tissue before cancer formed, suggesting the damage builds over time and creates a more vulnerable environment.
The team also identified an immune molecule, LILRB4, that acts as an “off switch” for the body’s cancer defenses. Disrupted sleep appeared to activate this pathway, making it harder for the immune system to fight tumors. When researchers blocked this signal, cancer spread slowed — even when sleep cycles remained disrupted. The findings raise concerns for shift workers and frequent travelers, while pointing to possible new ways to reduce cancer risk tied to chronic sleep disruption.
SOURCE:
Medical Xpress, December 23, 2025