A recent study indicates that artificial light entering your bedroom may be detrimental to your heart health.
Research set to be presented at the American Heart Association’s Scientific Sessions 2025 suggests that the level of darkness in which we sleep plays a critical role in our overall health. The findings link more artificial light at night with elevated brain stress, inflamed blood vessels, and even a higher risk of developing 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 through stress. Light pollution is very common; however, we don’t know much about how it affects the heart,” said study senior author Shady Abohashem, M.D., M.P.H., head of cardiac PET/CT imaging trials at Massachusetts General Hospital, in a November 3 release from the American Heart Association.
Abohashem and his team examined the health data of 466 adults who underwent the same combined Positron Emission Tomography/Computed Tomography (PET/CT) scan between 2005 and 2008. The scans, taken at Massachusetts General Hospital in Boston, were used to highlight stress signals in the brain and identify signs of inflammation in the arteries. The researchers also investigated the adults’ exposure to artificial nighttime brightness using the 2016 New World Atlas of Artificial Night Sky Brightness.
The people who were exposed to the most nighttime artificial light had higher brain stress activity, blood vessel inflation, and a greater chance of developing heart disease.
Moreover, people who lived in areas with added stress factors, like significant traffic noise, were at an even higher risk of heart issues.
“We found a nearly linear relationship between nighttime light and heart disease: the more night-light exposure, the higher the risk. Even modest increases in night-time light were linked with higher brain and artery stress,” Abohashem said.
Abohashem explained that when the brain identifies stress, it can trigger an immune response and drive inflamed blood vessels. Over an extended period, this can eventually contribute to arterial hardening and increase the likelihood of a cardiac event.
The solution?
Abohashem says cities could reduce unnecessary external lighting, and individuals should consider using their phones less before going to bed.