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Outdoor Light at Night Linked With Increased Breast Cancer Risk in Women

  • August 18, 2017

A long-term study of women living in areas with high levels of outdoor light at night shows that they may be at higher risk for breast cancer than those who aren’t exposed to similar lighting, according to researchers at Harvard T.H. Chan School of Public Health. Calling it the most comprehensive study yet on the topic, researchers said women exposed to such lighting had a 14 percent higher chance of breast cancer, with those working night shifts most at risk.

Light pollution, even exposure to very dim light while you sleep, is being found harmful more and more. That’s just one reason why I've been a long-time advocate of sleeping in TOTAL darkness. It has to do with the way your internal clock works: Based on signals of light and darkness, the suprachiasmatic nucleus (SCN) in your brain tells your pineal gland when it's time to secrete melatonin, and when to turn it off.

Your melatonin level inversely rises and falls with light and darkness, and both your physical and mental health are intricately tied to this rhythm of light and dark, and the connection between night shift work and cancer has been known for many years. When it's dark, your melatonin levels increase, which is why you may feel tired when the sun starts to set — signaling it’s time to get ready for sleep and rest.

Conversely, when you're exposed to bright artificial lighting at night, including blue light emitted from TVs and electronic screens, you may have trouble falling asleep due to suppressed melatonin levels, and ultimately this light can depress your pineal gland’s production of melatonin for the night.

Aside from seriously contemplating a job where you work only day shifts, one way to help yourself is to wear blue light-blocking glasses. They are inexpensive and far superior to traditional blue-blockers as they also filter out the yellow and green that can impair retinal health.