Too Much Light at Night Could Be Stressing Your Brain and Damaging Your Heart

There’s nothing worse than trying to fall asleep at night while the light from a nearby street lamp shines through your window. Beyond just being a nuisance, nighttime light pollution can have serious health effects, including increasing the risk of heart disease.

A recent presentation at the American Heart Association’s 2025 Scientific Sessions claims to have discovered the reason why nighttime light pollution negatively influences heart health: the more we are exposed to artificial light at night, the more stressed our brains become. This stress causes a chain reaction throughout the body, leading to inflammation of the arteries which can lead to heart disease.

“We know that too much exposure to artificial light at night can harm your health, including increasing the risk of heart disease. However, we did not know how this harm occurred,” Julio Fernandez-Mendoza, director of behavioral sleep medicine at the Pennsylvania State University College of Medicine, said in a press release. “This study investigated one of many possible causes, namely how our brains respond to stress. This response appears to play an important role in the link between artificial light at night and heart disease.”

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How can artificial light damage our hearts?

To study how light-induced nighttime stress increases heart disease risks, researchers analyzed data from 466 healthy Americans over a 10-year period. This data included patients’ medical records, brain and heart scans, and measurements of nighttime light activity in participants’ homes.

Most unique about this study was the use of a combined positron emission tomography/computed tomography (PET/CT) scanner.

According to Shady Abohashem, an instructor at Harvard Medical School, “using the two imaging techniques together makes it possible to measure brain stress activity and arterial inflammation in a single scan.”

This analysis, the first of its kind, revealed important details about the relationship between nighttime light pollution and heart disease:

• Higher levels of exposure to artificial light at night correlate with higher brain stress activity, increased blood vessel inflammation, and an overall higher risk of major cardiac events.
• Even the smallest increase in standard deviation could result in a 22 to 35 percent increase in heart disease risk over a five or ten year period.
• The risk of stress-related heart disease was even higher among people facing other environmental stressors in addition to nighttime light pollution, including traffic noise and low neighborhood income.

Overall, of the original 466 participants, 17 percent developed major heart problems by the end of the 10-year study.

How to Reduce Your Exposure to Nighttime Light

To reduce your personal exposure to nighttime light, Abohashem suggests “limiting nighttime light indoors, keeping bedrooms dark and avoiding screens such as televisions and personal electronics before bed.”

On a broader scale, the research team hopes their study results will inspire cities to take action by reducing outdoor lighting or installing motion-activated street lights. Ideally, they would like to see artificial light at night taken seriously as an environmental and public health issue.

“This research indicates that light pollution is more than just a nuisance; it could also increase the risk of heart disease. We hope that clinicians and policymakers will consider nighttime light exposure when developing prevention strategies,” Abohashem concluded.

This article does not offer medical advice and should be used for informational purposes only.

The study presented in this article is a research summary. Abstracts presented at American Heart Association scientific meetings are not peer-reviewed and results are considered preliminary until published as full manuscripts in a peer-reviewed scientific journal.

Learn more: Why light pollution is a crucial test of humanity’s problem-solving skills

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