New research presented at the American Heart Association’s Scientific Sessions 2025 indicates that exposure to artificial light at night may significantly increase the risk of heart disease. The observational study found a correlation between higher nighttime light levels, increased brain stress activity, blood vessel inflammation, and a heightened risk of major cardiac events. This suggests that even seemingly harmless exposure to light while sleeping could have detrimental effects on cardiovascular health.
The Link Between Light, Stress, and Heart Health
The study, involving 450 participants, utilized a combination of brain imaging and satellite measurements to assess light exposure and its impact over time. While the research doesn’t prove direct causation, it reveals a clear association between nighttime light exposure and adverse cardiovascular outcomes. The findings underscore the importance of maintaining a dark sleep environment to protect heart health.
Experts explain that light is a powerful biological signal that regulates the body’s internal clock, known as the circadian rhythm. Exposure to light at night disrupts this rhythm, suppressing melatonin production – a hormone vital for sleep regulation. This disruption activates stress centers in the brain, triggering inflammation in arteries, a known risk factor for heart disease.
“Our brains are wired to respond to natural light-dark cycles, and when those rhythms are disrupted, it can affect many systems in the body,” explains Shady Abohashem, MD, MPH, study co-author and head of Cardiac PET/CT Imaging Trials at Massachusetts General Hospital.
Why Nighttime Light Matters
The connection between light exposure and heart health stems from the body’s natural response to darkness. When exposed to light at night, the brain receives conflicting signals – it wants to sleep, but the light suggests it’s still daytime. This creates a “conflict” that disrupts sleep quality and triggers physiological stress.
W. Christopher Winter, MD, a neurologist and sleep medicine physician, emphasizes that this disruption isn’t just about feeling tired; it has real health consequences. “Being exposed to light at night creates a conflict between your brain wanting to sleep and getting a signal that it’s not time to sleep,” he explains.
Simple Steps to Protect Your Heart
Fortunately, mitigating the risks is straightforward. Experts recommend simple measures to ensure a dark sleep environment:
- Blackout Curtains: Block external light sources effectively.
- Sleep Masks: Provide darkness even in brightly lit rooms.
- Dimming Lights: Reduce artificial light exposure indoors.
These small changes can significantly improve sleep quality and protect cardiovascular health. “Protecting nighttime darkness may actually be part of protecting your heart,” says Dr. Abohashem.
The research reinforces the importance of prioritizing darkness during sleep, not just for better rest, but for long-term heart health. By minimizing light exposure at night, individuals can reduce stress, regulate melatonin production, and lower their risk of cardiovascular disease
