A new study reveals that high levels of artificial light at night are linked to increased stress-related brain activity, inflammation of the arteries, and a higher risk of heart disease.
The study was conducted by researchers from Harvard Medical School in the United States, and the results of the preliminary study will be presented at the 2025 scientific sessions of the American Heart Association, which will be held from the seventh to the tenth of this November in the city of New Orleans in the United States. The Eurek Alert website wrote about the study.
Artificial light at night, or night-time light pollution, is a near-universal feature of modern cities, and this study reviewed brain scans and satellite images to show a biological pathway linking night-time light exposure to heart disease.
“We know that environmental factors, such as air and noise pollution, can lead to heart disease by affecting our nerves and blood vessels as a result of stress,” said study co-author Dr. Shadi Abu Hashem, MPH, chief of cardiac PET/CT imaging trials at Massachusetts General Hospital, and lecturer at Harvard Medical School in Boston. “Light pollution is very common, however, we know little about how it affects the heart.”
Artificial brightness
This study included 450 adults without heart disease or any active cancer, and all participants underwent the same combined positron emission tomography/computed tomography (PET/CT) scan.
“This is a routine imaging exam at my hospital,” Abu Hashem said. “The CT portion provides detailed anatomy, while the PET portion detects metabolic activity in tissues. Using the two imaging techniques together allows brain stress activity and arterial inflammation to be measured in one scan.”
Light exposure data were obtained from the 2016 New World Atlas of Artificial Night Sky Brightness. Artificial brightness is defined as the brightness of the night sky at ground level, which is exclusively attributable to human-generated light sources, excluding natural sources such as starlight, airglow, and moonlight.
The amount of nighttime light in each person’s home was measured, as well as stress signals in the brain and markers of arterial inflammation in the scans.
People exposed to higher levels of artificial light at night had higher brain stress activity, inflammation in their blood vessels, and a higher risk of serious heart attacks.
Night light and heart disease
This information was collected from medical records and assessed by two cardiologists, who were unaware of any information that might influence their decisions.
The greater the exposure to artificial light at night, the greater the risk of heart disease. Additionally, heart disease risk was higher among participants who lived in areas with additional social or environmental stressors, such as loud traffic noise.
“We found a relationship between night light and heart disease: the more exposure to night light, the greater the risk,” Abu Hashim said. “Even small increases in night light were associated with higher brain and arterial pressure.”
When the brain feels stressed, it activates signals that trigger an immune response and cause inflammation of the blood vessels. Over time, this process can contribute to hardening of the arteries and increase the risk of heart attacks and strokes.
To combat the effects of artificial light at night, Abu Hashem suggested that cities reduce unnecessary outdoor lighting, cover streetlights, or use motion-sensitive lights.
He added: “People can limit indoor night lighting, keep bedrooms dark, and avoid screens such as televisions and personal electronic devices before bed.”