Circadian rhythms are the body’s 24-hour clock. They control sleep, hormone release, tissue repair and immune activity. A research team studied how repeated disruption of this clock affects breast tissue and cancer development.
The team used special mice that develop aggressive breast cancer. One group lived on a normal light–dark schedule. The other group lived on a disrupted light–dark cycle that threw off their internal clocks. The disrupted mice showed signs of cancer earlier and had more aggressive tumors that often spread to the lungs.
The disrupted schedule also weakened immune defenses and changed the structure of the milk-producing tissue, making it more vulnerable. The researchers say they will study whether these effects can be reversed in people who work nights or travel often.
Difficult words
- circadian rhythm — the body's natural 24-hour time cycleCircadian rhythms
- hormone — chemical in the body that sends messages
- tissue — group of similar cells in the body
- immune — related to the body's defense against diseaseimmune activity, immune defenses
- disruption — a change that stops normal function
- tumor — an abnormal growth in the bodytumors
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Discussion questions
- Have you or someone you know worked at night? How did it affect sleep or health?
- What can people do to keep a regular 24-hour routine when they travel?
- Why might changes in light and dark change the body's clock?
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