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 streetlamp beams through your window. Beyond just being a nuisance, nighttime light pollution can have serious health effects, including raising your risk of heart disease.

A recent presentation at the American Heart Association’s Scientific Sessions 2025 claims to have found the reason nighttime light pollution negatively influences heart health: the more exposure we have to artificial light during the night, the more stressed our brains become. This stress causes a chain reaction throughout the body, one result of which is inflamed arteries that can lead to heart disease.

“We know too much exposure to artificial light at night can harm your health, particularly increasing the risk of heart disease. However, we did not know how this harm happened,” said Julio Fernandez-Mendoza, director of behavioral sleep medicine at Pennsylvania State University College of Medicine, in a press release. “This study has investigated one of several possible causes, which is how our brains respond to stress. This response seems to play a big role in linking artificial light at night to heart disease.”

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How Can Artificial Light Damage Our Heart?

To investigate how nighttime light-induced stress increases the chances of heart disease, researchers analyzed data from 466 healthy Americans across a 10-year period. This data included the patients’ health records, brain and heart scans, and measurements of nighttime light activity within the participants’ homes.

Most unique to this study was the use of a combined Positron Emission Tomography/Computer Tomography (PET/CT) scan.

According to Shady Abohashem, an instructor at Harvard Medical School, “using both imaging techniques together allows for the measurement of brain stress activity and arterial inflammation in a single scan.”

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

• Higher levels of artificial light exposure at night correlated with higher brain stress activity, more inflammation in the blood vessels, and an overall higher risk of major cardiac events
• Even the smallest increase in standard deviation could cause a 22 to 35 percent increased risk of heart disease over a five- or 10-year period
• Stress-related heart disease risk was even higher for people who experienced other environmental stressors on top of the nighttime light pollution, including traffic noise and low neighborhood income

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

How To Lower Your Nighttime Light Exposure

To cut down on your personal nighttime light exposure, Abohashem suggests you “limit indoor nighttime light, keeping bedrooms dark and avoiding screens such as TVs and personal electronic devices before bed.”

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

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

This article is not offering medical advice and should be used for informational purposes only.

The study featured in this article is a research abstract. Abstracts presented at the American Heart Association’s scientific meetings are not peer-reviewed, and the findings are considered preliminary until published as full manuscripts in a peer-reviewed scientific journal.

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Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

• This article references information presented at the American Heart Association’s Scientific Sessions 2025: More exposure to artificial, bright, outdoor nighttime light linked to higher stroke risk