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 analyzed brain scans and medical records from more than 450 adults without existing heart disease.
Using PET/CT imaging, researchers observed brain stress activity and arterial inflammation in the participants. These two biological markers 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 results showed that people exposed to higher levels of artificial light at night had increased stress-related brain activity. This was especially true in regions that activate the body’s “fight-or-flight” response. That brain activity correlated with greater inflammation in the arteries, which is a key early driver of heart disease. Over time, 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 melatonin is only part of the story. When the brain perceives light at night, it does more than suppress melatonin. It activates the sympathetic nervous system, the part of the body that keeps a person alert and ready to respond to stress. That is useful during a real threat, but less ideal when lying in bed trying to rest. Over time, chronic activation of this “fight-or-flight” response can lead to inflammation, elevated blood pressure, and stiffer arteries. All of these increase cardiovascular risk.
To protect heart health and the body’s natural circadian rhythm, experts recommend making the bedroom a dark zone. Blackout curtains or a simple eye mask can block streetlight glow or flicker from passing cars. Even dim light can disrupt the body’s nightly repair processes. Switching to warm, amber-toned lighting in the evening can also help. Bright, blue-white LEDs should be saved for daytime when alertness is desired.
Phones, tablets, and TVs emit blue light that keeps the brain in daytime mode. Setting a “digital sunset” an hour before bed can help the body wind down naturally. For outdoor lighting, motion sensors or timers can reduce unnecessary brightness. These small changes may seem simple, but light exposure is one of the few environmental stressors that 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 new research adds to decades of evidence connecting circadian disruption with chronic disease. Protecting the heart might start with something as simple as turning off the lights.
