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  • With Mayo Clinic medical oncologist

    Timothy Moynihan, M.D.

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Question

Night shift and cancer: Any connection?

Does working the night shift increase the risk of cancer?

Answer

from Timothy Moynihan, M.D.

Various studies have suggested an association between night shift work and an increased risk of cancer, perhaps due to altered circadian rhythms or lower levels of melatonin in the blood. These studies haven't proved that shift work causes cancer, however. In fact, many of the studies linking shift work and cancer have serious limitations — such as difficulty controlling for known cancer risk factors, such as smoking.

If you work the night shift, switching to the day shift isn't likely to change your overall cancer risk. However, you can take other steps to help prevent cancer. For example:

  • Don't use tobacco.
  • Eat a variety of healthy foods.
  • Maintain a healthy weight.
  • Include physical activity in your daily routine.
  • Protect yourself from the sun.
  • Avoid alcohol, or limit alcohol consumption.
  • Avoid risky behaviors, such as sharing needles and having unprotected sex.
  • Reduce exposure to potentially hazardous substances, such as chemicals and harmful fumes.
  • Ask your doctor about vaccines for certain viral infections, such as hepatitis B.

Also remember the importance of regular screening and self-exams for certain types of cancer. Early detection increases the odds of successful treatment.

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References
  1. Moynihan T (expert opinion). Mayo Clinic, Rochester, Minn. Dec. 21, 2007.
  2. Mead MN. Shift work-cancer debate goes on. Environmental Health Perspectives. 2007;115:A535.
  3. Schernhammer ES, et al. Night work and risk of breast cancer. Epidemiology. 2006;17:108.
  4. Viswanathan AN, et al. Night shift work and the risk of endometrial cancer. Cancer Research. 2007;67:10618.

AN01941

Dec. 2, 2008

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