Women who work night shifts or frequently travel across time zones, leading to irregular sleep patterns, may face a higher risk of developing aggressive breast cancer, according to a new study.
Researchers from the Texas A&M University College of Arts and Sciences found that disruptions to the body’s circadian rhythm alter the structure of mammary glands and weaken immune system defences, creating conditions that allow cancer to grow and spread more easily.
“Cancer keeps time. If your internal clock is disrupted, cancer takes advantage — but now we’ve found a new way to fight back,” said Dr Tapasree Roy Sarkar, Co-Director of the Center for Statistical Bioinformatics at Texas A&M University College of Arts and Sciences.
Circadian rhythms — the body’s internal 24-hour clock — regulate not only sleep but also hormone release, tissue repair, and immune surveillance. When this rhythm is disturbed, the body’s natural defence mechanisms begin to fail.
“The circadian rhythm orchestrates how our tissues function and how the immune system recognises danger,” Sarkar said. “When that rhythm is disrupted, the consequences can be seriously dangerous.”
To study the impact, researchers used two groups of genetically engineered models prone to aggressive breast cancer. One group followed a normal day-night cycle, while the other was exposed to a disrupted light schedule that interfered with their internal clocks.
Findings published in the journal Oncogene showed that cancer typically developed around the 22-week mark in models with normal circadian rhythms. In contrast, those with disrupted cycles developed cancer much earlier, at around 18 weeks.
Tumours in the circadian-disrupted group were also significantly more aggressive and more likely to spread to the lungs — a key indicator of poor outcomes in breast cancer patients.
The study further found that disruption of the internal clock suppressed immune defences, creating a more favourable environment for tumour growth.
“It wasn’t just that the tumours grew faster,” Sarkar said. “The immune system was actively restrained, allowing cancer cells to survive and spread.”
Beyond tumour growth, long-term circadian disruption also altered healthy breast tissue, making it more susceptible to cancer.
“We observed clear changes in the morphology of the mammary glands — the milk-producing tissue of the breast,” Sarkar said.
–IANS
