A recent presentation at the American Heart Association’s Scientific Sessions 2025 suggests it has found the mechanism: increased exposure to artificial light at night stresses the brain, triggering a chain reaction that results in inflamed arteries—a precursor to heart disease.
The Stress-Inflammation Connection
Julio Fernandez-Mendoza, director of behavioral sleep medicine at Pennsylvania State University College of Medicine, explained that while the connection between artificial light at night and increased heart disease risk was established, the underlying mechanism was unknown.
He noted that this study focused on a key potential cause: "This study has investigated one of several possible causes, which is how our brains respond to stress. This seems to play a big role in linking artificial light at night to heart disease."
How Researchers Made the Discovery
Researchers analyzed 10 years of data from 466 healthy Americans, including health records, brain and heart scans, and measurements of nighttime light activity in their homes.
A unique and crucial aspect of this study was the use of a combined Positron Emission Tomography/Computer Tomography (PET/CT) scan.
According to Shady Abohashem, an instructor at Harvard Medical School, combining these two imaging techniques was essential. It allowed researchers to simultaneously measure brain stress activity and arterial inflammation in just one scan, providing a direct link between the two.
The first-of-its-kind analysis revealed several important connections:
- Higher artificial light exposure at night was correlated with three escalating factors: higher brain stress activity, more blood vessel inflammation, and an overall higher risk of major cardiac events.
- The data showed that even a small increase in light exposure could significantly impact health, potentially causing a 22 to 35 percent increased risk of heart disease over five or ten years.
- The risk of stress-related heart disease was amplified for individuals already facing additional environmental stressors, such as traffic noise and low neighborhood income.
Overall, 17 percent of the participants developed major heart conditions by the end of the 10-year study.
To mitigate personal risk, Shady Abohashem offers practical steps focused on individual behavior:
- Limit indoor nighttime light.
- Keep bedrooms dark.
- Switched off all electronic devices, such as TVs, mobile phones, and others, before bed.
On a broader scale, the research team hopes their findings will prompt cities and policymakers to act by:
- Reducing outdoor lighting or installing motion-activated streetlights.
- Formally recognizing artificial nighttime light as a serious environmental and public health issue.
Concluding the presentation, Abohashem stressed the significance of the findings:
"This research informed that light pollution is more than just an annoyance; it could increase the risk of heart disease. We expect clinicians and policymakers will consider night time light when developing prevention strategies."
Disclaimer: This content is published only for health awareness and informational purposes. It's not a substitute for your professional medical advice. You must consult a doctor/healthcare professional regarding your specific health concerns.
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