Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Cancer Health Center

Font Size

Night Shift Work May Cause Cancer

Studies Suggest Link Between Circadian Rhythm Disruption and Cancer
WebMD Health News
Reviewed by Louise Chang, MD

Nov. 30, 2007 -- Working the night shift may cause cancer, according to a report published in The Lancet.

The report comes from a team of 44 scientists in 10 countries commissioned by the World Health Organization's International Agency on Cancer Research.

They report "limited" evidence of a connection between cancer and night shift work in people. That evidence included a higher rate of breast cancer in female nurses who work night shifts.

But those studies, which were observational, don't prove cause and effect. Many genetic and environmental factors affect cancer risk.

So the scientists also reviewed studies in which animals were exposed to light at night, disrupting the animals' so-called body clocks (circadian rhythm).

Those studies provided "sufficient evidence" of a connection between circadian rhythm disruption and cancer, states the report.

The scientists concluded that "shift work that involves circadian rhythm disruption is probably carcinogenic to humans," write Kurt Straif, MD, and colleagues.

They note that shift work may raise cancer risk by suppressing production of melatonin, a chemical involved in the circadian rhythm.

Straif works in Lyon, France, for IARC.

The scientists also concluded working as a painter is carcinogenic and that working as a firefighter is "possibly carcinogenic" due to on-the-job chemical exposure.

Today on WebMD

Colorectal cancer cells
New! I AM Not Cancer Facebook Group
Lung cancer xray
See it in pictures, plus read the facts.
sauteed cherry tomatoes
Fight cancer one plate at a time.
Ovarian cancer illustration
Real Cancer Perspectives
Jennifer Goodman Linn self-portrait
what is your cancer risk
colorectal cancer treatment advances
breast cancer overview slideshow
prostate cancer overview
lung cancer overview slideshow
ovarian cancer overview slideshow
Actor Michael Douglas