Nighttime Light Pollution Linked to Increased Heart Disease Risk Through Brain Stress Response
A new study reveals that exposure to artificial light at night increases heart disease risk by triggering stress-related brain activity and arterial inflammation, highlighting light pollution as a modifiable environmental health factor.
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. The research, conducted at Massachusetts General Hospital in Boston, represents the first investigation to demonstrate a biological pathway connecting nighttime light exposure to cardiovascular health problems.
The study analyzed 450 adults without pre-existing heart disease or active cancer who underwent combined Positron Emission Tomography/Computed Tomography (PET/CT) scans between 2005 and 2008. Researchers 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. The analysis revealed a nearly linear relationship between nighttime light exposure and heart disease risk, with every standard deviation increase in light exposure associated with approximately 35% and 22% increased risk of heart disease over five- and ten-year follow-up periods, respectively.
Study senior author Shady Abohashem, M.D., M.P.H., head of cardiac PET/CT imaging trials at Massachusetts General Hospital, explained the mechanism behind this connection. "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 findings remained significant even after accounting for traditional risk factors and other socio-environmental exposures like noise pollution and socioeconomic status.
The research utilized 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. During the ten-year follow-up period, 17% of participants developed major heart conditions, with higher risks observed among those living in areas with additional social or environmental stress factors such as high traffic noise or lower neighborhood income.
Julio Fernandez-Mendoza, Ph.D., who serves on the writing committee of the American Heart Association's scientific statement on Multidimensional Sleep Health: Definitions and Implications for Cardiometabolic 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 study's implications extend to both public policy and individual behavior. Abohashem suggested that cities could reduce unnecessary outdoor lighting, shield streetlamps or use motion-sensitive lights to mitigate the effects of artificial light at night. On a personal level, he recommended that people limit indoor nighttime light, keep bedrooms dark and avoid screens such as TVs and personal electronic devices before bed. The American Heart Association recently issued a scientific statement on the Role of Circadian Health in Cardiometabolic Health and Disease Risk, which also identified light pollution as a major factor disrupting body clocks and increasing cardiovascular disease risk.
While the study provides important insights, researchers caution that it has several limitations. As an observational analysis of previously collected information, it cannot prove direct cause-and-effect relationships. Additionally, the participant group came from only one hospital system and was predominantly white (89.7%), meaning the findings may not be generalizable to more diverse populations. The research team plans to expand this work in larger, more diverse populations and test interventions that reduce nighttime light exposure to determine how such measures might improve heart health outcomes.