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 nighttime light 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 people exposed to higher levels of artificial light at night had increased stress-related brain activity, particularly in regions that activate the body’s “fight-or-flight” response. This brain activity correlated with greater inflammation in the arteries, a key early driver of heart disease. Over time, these biological signals translated into a significantly higher risk of cardiovascular events.
Light at night affects more than just melatonin, the hormone that tells the body it is time to sleep. When the brain perceives light at night, it activates the sympathetic nervous system, which keeps the body alert and ready to respond to stress. Chronic activation of this “fight-or-flight” response can lead to inflammation, elevated blood pressure, and stiffer arteries, all of which increase cardiovascular risk.
To protect heart health and circadian rhythm, experts recommend making the bedroom a dark zone using blackout curtains or an eye mask. Switching to warm, amber-toned lighting in the evening instead of bright, blue-white LEDs can help. Setting a “digital sunset” an hour before bed by avoiding phones, tablets, and TVs can also reduce blue light exposure. For outdoor lighting, using motion sensors or timers can reduce unnecessary brightness.
Light exposure is one of the few environmental stressors people can directly control. Artificial light at night does not just interfere with sleep; it may quietly strain the cardiovascular system in ways that build up over time. This research adds to decades of evidence connecting circadian disruption with chronic disease, suggesting that protecting heart health might start with something as simple as turning off the lights.
