Nighttime Light Pollution Linked to Increased Heart Disease Risk Through Brain Stress Response

Higher levels of exposure to 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 to be presented at the American Heart Association's Scientific Sessions 2025. This first-of-its-kind study reviewed brain scans and satellite images to show a biological pathway linking nighttime light exposure to heart disease, with researchers finding a nearly linear relationship between nighttime light exposure and heart disease risk.

The study of 450 adults without heart disease or active cancer used combined Positron Emission Tomography/Computed Tomography (PET/CT) scans to measure brain stress activity and arterial inflammation. 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. 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, even after accounting for traditional risk factors and other socio-environmental exposures.

Study senior author Shady Abohashem, M.D., M.P.H., head of cardiac PET/CT imaging trials at Massachusetts General Hospital, explained the mechanism: "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 heart risks were higher among participants who lived in areas with additional social or environmental stress, such as high traffic noise or lower neighborhood income.

Researchers obtained exposure data from the 2016 New World Atlas of Artificial Night Sky Brightness, which integrates upward radiance data from satellite imaging to estimate ground-level zenith sky brightness. The study participants were scanned between 2005 and 2008 and retrospectively followed up to the end of 2018, during which 17% of participants developed major heart problems.

Julio Fernandez-Mendoza, Ph.D., who serves on the writing committee of the American Heart Association's scientific statement on Multidimensional Sleep Health, noted the significance of these findings. "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. This study has investigated one of several possible causes, which is how our brains respond to stress."

The research adds to growing evidence about the health impacts of light pollution, coming just after the Association issued a scientific statement on the Role of Circadian Health in Cardiometabolic Health and Disease Risk that also identified light pollution as a major factor disrupting body clocks and increasing cardiovascular disease risk. While the study has limitations as an observational analysis from a single hospital system, it provides important insights into how environmental factors affect heart health through neurological pathways.

Abohashem suggested practical interventions to counter the effects of artificial light at night, including cities reducing unnecessary outdoor lighting, shielding streetlamps or using motion-sensitive lights. On a personal level, people can limit indoor nighttime light, keep bedrooms dark and avoid screens before bed. The findings indicate that light pollution represents more than just an annoyance and could be an important environmental factor that communities could modify to help reduce heart disease risk.