Turn off the lights!

Nighttime brightness may be harmful to your health

Created date

February 12th, 2018
A crew member aboard the International Space Station photographed this night image of Paris, France, in 2013.

A crew member aboard the International Space Station photographed this night image of Paris, France, in 2013.


Every summer, armchair astronomers look forward to the spectacle known as the Perseid meteor shower. But with each passing year, the celestial display is getting harder to see. 

Meteor showers like the Perseids are best seen in a dark sky, and truly dark skies are increasingly hard to come by. 

At issue is light pollution brought on by the use and overuse of artificial light at night. The sprawl of population centers has dramatically increased the number of areas requiring nighttime illumination, and new technology has made brighter light cheaper and more accessible. 

Light pollution

According to a report issued by GFZ German Research for Geosciences in Potsdam, Germany, light pollution is blurring our view of the sky. Artificially lit outdoor areas grew by 2.2% between 2012 and 2016.  

The report found that nighttime brightness grew in 79 nations, primarily in South America, Asia, and Africa, and nighttime brightness diminished in only 16 nations—mainly those impacted by war or disaster, such as Syria and Yemen. 

The nighttime brightness in 39 countries, including the U.S., remained the same.  

“Light is growing most rapidly in places that didn’t have a lot of light to start with,” says Dr. Christopher Kyba, a lead author of the study. “That means that the fastest rates of increase are occurring in places that so far hadn’t been very strongly affected by light pollution.”


One reason for the recent increase in nighttime brightness is the growing popularity of LEDs (light emitting diodes). Far more efficient than older light technology, LEDs provide a bright white light that can illuminate outdoor spaces like nothing else. Unfortunately, the light from LEDs also contains a lot of blue, and blue brightens the night sky more than any other color. 

Another issue with LEDs is the cost. Initially, LEDs were expensive, but the cost has come down significantly. In theory, cities and towns switching to LEDs for outdoor public spaces should see a decrease in energy expenditures…but that hasn’t happened. Instead, the affordability of LEDs has many communities adding more light.

Animal impact

Beyond inconveniencing stargazers, a brighter earth has serious implications that can ultimately impact creatures up and down the food chain. 

For example, artificial light attracts insects, diverting them from their normal habitats. When that happens, creatures who eat insects such as fish or reptiles are suddenly left without a food supply. 

Studies have shown that light pollution impacts everything from sea turtles to migrating birds. That is why the National Park Service makes a concerted effort to minimize the impact of artificial light on the wildlife within its parks.

Human impact

Light pollution is also impacting humans. Recent large surveys found that brighter residential nighttime lighting is associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning, and obesity.

In 2016, the American Medical Association (AMA) published a report about LEDs and human health. It found that blue color in LED lighting creates glare, which can significantly impact the safety of nighttime driving. 

They also found that LED street lights emit a wavelength found to suppress human melatonin, a hormone related to sleep. Perhaps most alarmingly, the report estimates that white LED lamps have five times greater impact on circadian sleep rhythms than conventional street lamps. 

“Despite the energy efficiency benefits, some LED lights are harmful when used as street lighting,” says AMA Board Member Maya A. Babu, M.D., M.B.A. 

The report included recommendations about the use of LEDs. “The new AMA guidance encourages proper attention to optimal design and engineering features when converting to LED lighting that minimize detrimental health and environmental effects,” says Babu.

Nobel Prize

The study of light and its impact on living things received an important vote of confidence when the 2017 Nobel Prize in Physiology or Medicine was awarded jointly to Jeffrey C. Hall, Michael Rosbash and Michael W. Young “for their discoveries of molecular mechanisms controlling the circadian rhythm.” 

“Until quite recently, circadian biology was considered a quaint little subtopic of biology in general,” says Dr. Richard G. Stevens, professor of community medicine and health care at UConn Health. “However, the 2017 Nobel Prize for discovery of the mechanisms controlling circadian rhythmicity highlights the fact that circadian biology is fundamental to all biology in almost all organisms on the planet.”

“Electric light that is too bright and too blue at the wrong time of day disrupts our circadian rhythmicity,” says Stephens. “Using it unwisely is the most potent source of ‘misalignment’ in the modern world.”

For information about how to minimize the impact of nighttime lighting, visit darksky.org.