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.
Researchers used PET/CT imaging to observe brain stress activity and arterial inflammation in participants. They also mapped how much artificial light each person 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. This was especially true in regions that activate the body’s “fight-or-flight” response. That brain activity was linked to greater inflammation in the arteries, which is an early sign of heart disease.
Over time, these biological signals translated into a higher risk of cardiovascular events. The brain appears to interpret nighttime light as a form of stress, which can start a chain reaction that affects the heart.
Light at night does more than suppress 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, keeping the body alert and ready to respond to stress. Chronic activation of this response can lead to inflammation, elevated blood pressure, and stiffer arteries.
To reduce these risks, experts suggest making the bedroom a dark zone with blackout curtains or an eye mask. Switching to warm, amber-toned lighting in the evening can also help. Bright, blue-white LEDs should be saved for daytime use. Setting a curfew for phones, tablets, and TVs an hour before bed may allow the body to wind down naturally. Outdoor lights with motion sensors or timers can reduce unnecessary brightness at night.
This research adds to decades of evidence connecting disrupted circadian rhythms with chronic disease. Protecting heart health may start with simple changes to nighttime light exposure.
