Exposure to artificial light at night may significantly increase the risk of heart disease by triggering stress-related brain activity and arterial inflammation, according to preliminary research presented at the American Heart Association’s Scientific Sessions 2025. The study, which analyzed brain scans and satellite data from 466 adults in Boston, found that higher levels of nighttime light pollution were associated with a nearly linear increase in cardiovascular risk, independent of traditional risk factors and other environmental stressors like noise pollution.
“We found that 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. “When the brain perceives stress, it activates signals that can trigger an immune response and inflame the blood vessels. Over time, this process can contribute to hardening of the arteries and increase the risk of heart attack and stroke.”
The research, which is considered preliminary until published in a peer-reviewed journal, used combined Positron Emission Tomography/Computed Tomography (PET/CT) scans to measure brain stress activity and arterial inflammation in participants without pre-existing heart disease or active cancer. Exposure to artificial light at night was estimated using data from the 2016 New World Atlas of Artificial Night Sky Brightness, which integrates satellite radiance data with radiative transfer modeling.
Over a 10-year follow-up period, 17% of participants experienced major heart conditions. The analysis showed that every standard deviation increase in light exposure was associated with about a 35% increased risk of heart disease over five years and a 22% increased risk over 10 years. These associations remained significant after adjusting for traditional risk factors, noise pollution, and socioeconomic status. Notably, the risks were even higher among individuals living in areas with additional social or environmental stress, such as high traffic noise or lower neighborhood income.
“These findings are novel and add to the evidence suggesting that reducing exposure to excessive artificial light at night is a public health concern,” said Julio Fernandez-Mendoza, Ph.D., DBSM, FAHA, a professor of psychiatry, neuroscience and public health sciences at Pennsylvania State University College of Medicine, who was not involved in the study. He noted that the American Heart Association recently issued a scientific statement on the Role of Circadian Health in Cardiometabolic Health, which indicates that light pollution disrupts body clocks, suppresses melatonin, and increases cardiovascular disease risk.
While the study is observational and cannot prove causation, it offers a plausible biological pathway linking light pollution to heart disease. The researchers suggest that cities could 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.
“We want to expand this work in larger, more diverse populations, test interventions that reduce nighttime light, and explore how reducing light exposure might improve heart health,” Abohashem said. The study underscores the potential of addressing light pollution as a modifiable environmental factor for cardiovascular prevention, particularly in communities with high levels of nighttime illumination.
