Light at Night and Human Health


The Relationship Between Obesity and Exposure to Light at Night: Cross-Sectional Analyses of Over 100,000 Women, Emily McFadden, Michael E. Jones, Minouk J. Schoemaker, Alan Ashworth and Anthony J. Swerdlow March, 2014

There has been a worldwide epidemic of obesity in recent decades. In animal studies, there is convincing evidence that light exposure causes weight gain, even when calorie intake and physical activity are held constant. Disruption of sleep and circadian rhythms by exposure to light at night (LAN) might be one mechanism contributing to the rise in obesity, but it has not been well-investigated in humans. Using multinomial logistic regression, we examined …

short wavelength and vision

Sensitivity of the Human Circadian System to Short-Wavelength (420 nm) Light, G.C. Brainard et al. Journal of Biological Rhythms, 23(5), 379, 2008

The circadian and neurobehavioral effects of light are primarily mediated by a retinal ganglion cell photoreceptor in the mammalian eye containing the photopigment melanopsin. Nine action spectrum studies using rodents, monkeys, and humans for these responses indicate peak sensitivities in the blue region of the visible spectrum ranging from 459 to 484 nm, with some disagreement in short-wavelength sensitivity of the spectrum. The aim of this work was to quantify the sensitivity of human volunteers to monochromatic 420-nm light for plasma melatonin suppression. Adult …

Human Health and Blue White Light

What’s In A Color? The Unique Human Health Effects of Blue Light David C. Holzman, Environmental Health Perspectives; 118(1): A22–A27, January, 2010

Coming Full Circle:
The irony of blue as an environmental agent is that before the industrial age, it was merely a color. The unnatural lighting conditions we created turned it into both a potential hazard and a treatment for the ailments it brought about. In addition to the traditional architectural values of visual comfort, aesthetics, and energy efficiency, Brainard says architectural lighting must be redesigned to account for its biological and behavioral impact on humans. “Ultimately that should improve …”


Blue light has a dark side Harvard Health Letter, May 2012

Light at night is bad for your health, and exposure to blue light emitted by electronics and energy-efficient lightbulbs may be especially so.


To celebrate, promote, and protect the glorious dark skies of Flagstaff and northern Arizona.