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. The research, conducted at Massachusetts General Hospital, represents the first investigation to demonstrate a biological pathway connecting nighttime light exposure to cardiovascular 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 used satellite data from the 2016 New World Atlas of Artificial Night Sky Brightness to measure nighttime light exposure at participants' homes while assessing brain stress activity and arterial inflammation through advanced imaging techniques.

Findings revealed a nearly linear relationship between artificial night light exposure and heart disease risk. Every standard deviation increase in light exposure was associated with approximately 35% and 22% increased risk of heart disease over five- and ten-year follow-up periods, respectively. These associations persisted even after accounting for traditional risk factors and other environmental exposures like noise pollution and socioeconomic status.

"We found a nearly linear relationship between nighttime light and heart disease: the more night-light exposure, the higher the risk," 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 gains additional significance in light of recent scientific statements from the American Heart Association, including last week's statement on the Role of Circadian Health in Cardiometabolic Health and Disease Risk. That statement also identified light pollution as a major factor disrupting body clocks and potentially increasing cardiovascular disease risk.

Julio Fernandez-Mendoza, Ph.D., who served on the writing committee for the Association's multidimensional sleep health statement, noted the importance 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," said Fernandez-Mendoza, who was not involved in the study. "This study has investigated one of several possible causes, which is how our brains respond to stress."

The study's implications extend beyond individual health to broader public policy considerations. Researchers suggest that cities could reduce unnecessary outdoor lighting, shield streetlamps, or use motion-sensitive lights to mitigate the effects. On a personal level, individuals can limit indoor nighttime light, keep bedrooms dark, and avoid screens before bed.

During the ten-year follow-up period, 17% of participants developed major heart conditions. The heart risks appeared higher among participants living in areas with additional social or environmental stress factors, such as high traffic noise or lower neighborhood income.

While the study represents an important advancement in understanding environmental influences on heart health, researchers note limitations including its observational nature and the predominantly white participant population from a single hospital system. The findings are considered preliminary until published as a full manuscript in a peer-reviewed scientific journal.

"This research indicates that light pollution is more than just an annoyance; it could also increase the risk of heart disease," Abohashem concluded. "We hope clinicians and policymakers will consider nighttime light exposure when developing prevention strategies."