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Artificial Light Stimulates Breast Cancer Tumors

woman staring at a computer screen

NIEHS-funded research showed that nighttime exposure to artificial light can stimulate the growth of breast tumors in mice by suppressing the levels of a key hormone called melatonin. Blood extracted from sleeping volunteers could actually prevent tumor growth in an animal model. Extended periods of nighttime darkness were shown to greatly slow the growth of these tumors. Blood from women whose sleep was interrupted lost much of its cancer-prevention ability. These results might explain why female night shift workers have a higher rate of breast cancer, and may offer an explanation for the rise in breast cancer incidence in industrialized countries.

Tags: breast cancer, women's health


Blask DE, Brainard GC, Dauchy RT, Hanifin JP, Davidson LK, Krause JA, Sauer LA, Rivera-Bermudez MA, Dubocovich ML, Jasser SA, Lynch DT, Rollag MD, Zalatan F. 2005. Melatonin-depleted blood from premenopausal women exposed to light at night stimulates growth of human breast cancer xenografts in nude rats. Cancer Res 65(23):11174-11184. [Abstract] [Full Text]

More Information:

NIEHS Research Funding:

  • Breast Cancer & the Environment Research Centers
  • Who We Fund 

 News Release:

  • 2005: Artificial Light at Night Stimulates Breast Cancer Growth in Laboratory Mice

 Environmental Health Perspectives articles:

 Health Information:


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