A new study funded by the American Heart Association (AHA) has found that exposure to artificial light at night may significantly increase the risk of developing heart disease.
Researchers at Massachusetts General Hospital in Boston analyzed data from 466 adults—with a median age of 55—who had undergone PET/CT brain scans between 2005 and 2008. These scans measured brain stress activity and arterial inflammation, both early indicators of cardiovascular problems.
Scientists then cross-referenced participants’ brain and heart data with satellite images showing the brightness levels around their homes, using the 2016 New World Atlas of Artificial Night Sky Brightness to assess exposure.
By 2018, follow-up results revealed that 79 participants (17%) had developed major heart issues. The findings showed a clear correlation — the greater the exposure to nighttime artificial light, the higher the brain stress activity, blood vessel inflammation, and overall heart disease risk.
Study author Dr. Shady Abohashem, head of cardiac PET/CT imaging trials at Massachusetts General Hospital, described the relationship as “nearly linear.”
“Even modest increases in night-time light were linked with higher brain and artery stress,” Dr. Abohashem said. “When the brain perceives stress, it triggers immune responses that inflame blood vessels. Over time, this can harden arteries and increase the risk of heart attack and stroke.”
The study found that light exposure raised the risk of heart disease by 35% over five years and 22% over ten years. Risks were also higher among people living in noisy or high-stress urban environments.
Dr. Abohashem suggested that cities could reduce unnecessary outdoor lighting, install motion-sensitive streetlights, and encourage individuals to keep bedrooms dark and avoid screens before bedtime.
“Light pollution is more than just an annoyance — it’s a real public health concern,” he said. “We hope these findings prompt clinicians and policymakers to consider nighttime light exposure in heart disease prevention.”
While the researchers cautioned that this was an observational study—meaning it could not prove direct cause and effect—the results add to growing evidence that artificial light exposure disrupts the body’s circadian rhythm, increasing the risk of coronary artery disease, heart failure, and stroke.
The study will be presented at the American Heart Association’s Scientific Sessions in New Orleans later this week.
