Exposure to artificial light at night is linked to heightened stress in the brain, inflammation in arteries, and an increased risk of heart disease, according to a new study presented at the American Heart Association’s Scientific Sessions 2025. This research suggests that nighttime light pollution is a measurable environmental factor impacting cardiovascular health.
The Connection Between Light and Heart Health
Researchers combined brain imaging and satellite measurements to identify a biological pathway connecting nighttime brightness with heart disease risk. The study, conducted on 466 adults in Boston, found that higher exposure to artificial light at night correlated with increased stress signals in the brain and inflammation in blood vessels. These factors collectively elevate the risk of developing heart problems over time.
“We know environmental factors like air and noise pollution affect the heart through stress. Light pollution is common, but its impact on the heart was previously unclear,” explains Dr. Shady Abohashem, the study’s senior author from Massachusetts General Hospital.
How Nighttime Light Impacts the Body
The study leveraged advanced PET/CT scans to measure brain stress activity and arterial inflammation simultaneously. Results showed that every increase in light exposure was associated with a 35% to 22% higher risk of heart disease over five- and ten-year periods. This correlation persisted even after accounting for traditional risk factors like socioeconomic status and noise pollution.
The mechanism appears to involve the brain’s stress response, triggering inflammation in blood vessels over time, potentially leading to hardening of the arteries and increased risk of heart attack or stroke.
What This Means for Public Health
The findings reinforce growing evidence that excessive artificial light at night is a public health concern. Cities could reduce unnecessary outdoor lighting, shield streetlamps, or use motion-sensitive lights to mitigate this effect. On an individual level, limiting indoor nighttime light—keeping bedrooms dark and avoiding screens before bed—may also help.
“This study has investigated one of several possible causes, which is how our brains respond to stress,” says Dr. Julio Fernandez-Mendoza, a sleep health expert at Pennsylvania State University College of Medicine. “This response seems to play a big role in linking artificial light at night to heart disease.”
Study Limitations and Future Research
It is important to note that this is an observational study and cannot prove direct cause-and-effect. The participant group (89.7% white) may not be representative of the broader population. Further research is needed in larger, more diverse populations to confirm these findings and test interventions to reduce nighttime light exposure.
However, the study adds to growing evidence that reducing exposure to excessive artificial light at night is a public health concern and may improve heart health.
