Researchers from Massachusetts General Hospital in Boston, presenting at the American Heart Association’s Scientific Sessions 2025, have found that even modest nighttime brightness could increase stress signals in the brain and inflammation in blood vessels ehich are two factors linked to heart disease.
The study and its findings
The team analyzed data from about 450 adults who had no previous heart conditions.
Using PET/CT scans, they measured brain activity related to stress and inflammation in the arteries.
Satellite data provided details about how much artificial light surrounded each participant’s home.
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Those living in brighter areas showed higher brain stress activity and more vessel inflammation.
Over a ten-year follow-up, nearly one in five developed major heart problems.
According to lead researcher Dr. Shady Abohashem, artificial light appears to act as an environmental stressor, similar to air or noise pollution.
When the brain stays alert due to constant light, the body’s natural rest cycles are disrupted, which may trigger chronic inflammation and damage to the cardiovascular system.
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Who faces the greatest risk?
The connection between light exposure and heart problems was strongest in people who lived in neighborhoods with other sources of stress, such as heavy traffic or lower income levels.
These overlapping pressures may intensify how the body responds to artificial light at night.
What can be done
While the study cannot prove a direct cause-and-effect link, researchers say the results highlight the need to reduce unnecessary lighting.
Simple actions, such as turning off screens before bed, using blackout curtains, or installing motion-sensitive outdoor lights, can help lower exposure.
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Experts also urge city planners to design lighting systems that limit sky glow and protect public health.
Darkness, they note, is not just important for good sleep, it may also help keep the heart healthy.
Sources: Sciencedaily.com, and Newsroom.heart.org.
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