New research presented at the American Heart Association’s 2025 Scientific Sessions suggests that exposure to artificial light at night may increase the risk of heart disease. The study found that people exposed to higher levels of artificial light at night showed increased stress-related brain activity and greater inflammation in the arteries.
Researchers analyzed brain scans and medical records from more than 450 adults without existing heart disease. Using PET/CT imaging, they observed brain stress activity and arterial inflammation, two biological markers that often appear years before cardiovascular disease develops. The team then mapped how much artificial light each participant was exposed to at night based on their home address.
The findings showed that the brain appears to interpret nighttime light as a form of stress. This activates the body’s “fight-or-flight” response, which over time can lead to inflammation, elevated blood pressure, and stiffer arteries. These biological signals translated into a higher risk of cardiovascular events.
Light affects melatonin, the hormone that tells the body it is time to sleep. But the study suggests that light does more than suppress melatonin. When the brain perceives light at night, it activates the sympathetic nervous system, keeping the body alert and ready to respond to stress. Chronic activation of this response can wear down the heart over time.
To protect heart health, experts recommend making the bedroom a dark zone using blackout curtains or an eye mask. Switching to warm, amber-toned lighting in the evening can also help. Bright, blue-white LEDs should be reserved for daytime when alertness is desired. Phones, tablets, and TVs emit blue light that keeps the brain in daytime mode, so setting a “digital sunset” an hour before bed may help the body wind down naturally. Outdoor lights can be fitted with motion sensors or timers to reduce unnecessary brightness.
The research adds to decades of evidence connecting circadian disruption with chronic disease. Light exposure is one of the few environmental stressors that people can directly control, and small changes may help reduce long-term strain on the cardiovascular system.
