The Effects of Blue Light on Circadian Disruption, Possibly Leading to Increased Breast Cancer Risk

Overexposure to light at night may be contributing to breast cancer rates among women worldwide. This hypothesis is based on the idea that exposure to light at night results in melatonin suppression which could, in turn, increase breast cancer risk.

According to the study Breast Cancer and Circadian Disruption from Electric Lighting in the Modern World published by the National Health Institute, “A convergence of research in cells, rodents, and humans suggests that the health consequences of circadian disruption may be substantial. An innovative experimental model has shown that light at night markedly increases the growth of human breast cancer xenografts in rats.

The strongest evidence supporting this hypothesis to date is data showing that women who regularly work nights shifts are at higher risk of breast cancer. The study also provided evidence that blind women may be at lower risk of breast cancer due to their inability to detect light.

Electric lighting rich in blue wavelengths is most effective in disrupting circadian rhythmicity, affecting one’s melatonin production, sleep and the circadian clock. Blue wavelengths can also be harmful to your eye safety and overall well-being, even the display screens of personal computers can alter melatonin production in the evening. Unnecessary exposure to light rich in the blue portion of the visible spectrum may be a contributing factor in breast cancer rates among women.

It has been shown that under carefully controlled conditions, retinal exposure to illuminances of as low as 1 lux or less of monochromatic light at wavelength 440–460 (blue appearing light) can significantly lower nocturnal melatonin, as can <100 lux of broad-spectrum fluorescent light,” the study states. “These same light levels can also elicit significant phase shifts of the circadian clock and directly enhance alertness.

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