Nighttime Light Exposure Linked to Increased Heart Disease Risk, Study Finds

New research presented today suggests a direct correlation between exposure to artificial light at night and increased risk of heart disease, brain stress, and inflammation of blood vessels.

A preliminary analysis, set to be fully presented at the American Heart Association’s Scientific Sessions 2025 starting Friday, reviewed data from 466 adults who underwent PET/CT scans between 2005 and 2008 at Massachusetts General Hospital in Boston. Researchers, led by Shady Abohashem, head of cardiac PET/CT imaging trials at Massachusetts General Hospital, cross-referenced scan results – identifying brain stress signals and artery inflammation – with participants’ exposure to artificial nighttime brightness using the 2016 New World Atlas of Artificial Night Sky Brightness. The findings revealed a “nearly linear relationship” between nighttime light and heart disease, with even modest increases in exposure linked to higher stress levels in the brain and arteries.

“We found a nearly linear relationship between nighttime light and heart disease: the more night-light exposure, the higher the risk,” Abohashem said in a statement. “Even modest increases in night-time light were linked with higher brain and artery stress.” The study also noted that existing stressors, such as traffic noise and lower neighborhood income, amplified the risk. By 2018, 17% of participants had experienced significant heart problems. This research adds to a growing body of evidence highlighting the importance of sleep hygiene for overall cardiovascular health; poor sleep is already a known risk factor for heart conditions.

Experts suggest both cities and individuals can take steps to mitigate the risks. Reducing unnecessary external lighting and limiting screen time before bed are key recommendations. Julio Fernandez-Mendoza, director of behavioral sleep medicine at Pennsylvania State University College of Medicine, who was not involved in the study, explained, “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.” For more information on the impact of light on health, see the National Institute of Environmental Health Sciences.

Abohashem stated that further research is planned to expand the study to more diverse populations, test interventions to reduce nighttime light exposure, and explore potential improvements to heart health.