Higher levels of artificial light at night were linked to increased stress-related activity in the brain, inflamed arteries, and a higher risk of heart disease, according to a preliminary study presented at the American Heart Association's Scientific Sessions 2025.

Artificial light at night, or nighttime light pollution, is a nearly universal feature of modern cities, according to the study. This first-of-its-kind study reviewed brain scans and satellite images to show a biological pathway linking nighttime light exposure to heart disease.

"We know that environmental factors, such as air and noise pollution, can lead to heart disease by affecting our nerves and blood vessels through stress. Light pollution is very common; however, we don't know much about how it affects the heart," said study senior author Shady Abohashem, head of cardiac PET/CT imaging trials at Massachusetts General Hospital and an instructor at Harvard Medical School in Boston.

450 adult patients underwent identical PET/CT scans, and all of whom were without heart disease and no active cancer.

"This is a routine imaging test at my hospital," Abohashem said. "The CT portion provides detailed anatomy, while the PET portion reveals metabolic activity in tissues. Using both imaging techniques together allows for the measurement of brain stress activity and arterial inflammation in a single scan."

The analysis found that people exposed to higher levels of artificial light at night had higher brain stress activity, blood vessel inflammation and a higher risk of major heart events.

This information was collected from medical records and evaluated by two cardiologists who were blinded, meaning they were unaware of any information that could influence their decisions.

The greater the artificial night light exposure, the higher the risk of heart disease development. Every standard deviation increase in light exposure was associated with about 35% and 22% increased risk of heart disease over five- and 10-year follow-up periods, respectively.