A study to be presented at the American Heart Association’s Scientific Sessions 2025, Nov. 7-10 in New Orleans, reveals a biological link between artificial light at night and heart disease. Researchers analyzed brain scans and satellite data from 466 adults without prior heart disease and found that higher nighttime light exposure correlated with increased stress-related brain activity, inflamed arteries, and a higher risk of major cardiac events over a 10-year follow-up.
“We found a nearly linear relationship between nighttime light and heart disease: the more night-light exposure, the higher the risk. Even modest increases in night-time light were linked with higher brain and artery stress,” said study senior author Shady Abohashem, M.D., M.P.H., head of cardiac PET/CT imaging trials at Massachusetts General Hospital and an instructor at Harvard Medical School in Boston. The study used combined PET/CT scans to measure brain stress and arterial inflammation, alongside satellite data from the 2016 New World Atlas of Artificial Night Sky Brightness.
Results showed that 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. These associations persisted after adjusting for traditional risk factors and socio-environmental exposures like noise pollution and socioeconomic status. Over the follow-up, 17% of participants experienced major heart conditions. The study also found that heart risks were higher among those living in areas with additional social or environmental stress, such as high traffic noise or lower neighborhood income.
“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,” Abohashem said. The findings suggest a pathway where the brain perceives stress from light pollution, activating signals that trigger immune responses and inflame blood vessels, leading to atherosclerosis and increased risk of heart attack and stroke.
Julio Fernandez-Mendoza, Ph.D., DBSM, FAHA, a professor at Pennsylvania State University College of Medicine and member of the American Heart Association’s Multidimensional Sleep Health writing committee, commented, “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.” He noted that the American Heart Association’s recent scientific statement on circadian health also identifies light pollution as a major factor disrupting body clocks and increasing cardiovascular risk.
To mitigate effects, Abohashem suggested cities reduce unnecessary outdoor lighting, shield streetlamps, or use motion-sensitive lights. On a personal level, people can limit indoor nighttime light, keep bedrooms dark, and avoid screens before bed. The study is considered preliminary until published in a peer-reviewed journal, and its observational nature precludes establishing causation. Limitations include a predominantly white sample from a single hospital system, limiting generalizability. Researchers aim to expand work in diverse populations and test interventions to reduce nighttime light exposure.
