Quick Facts

• Adults exposed to higher nighttime artificial light had a 35% increased risk of heart disease within five years
• Light pollution activates brain stress responses that cause arterial inflammation throughout the body
• Simple changes like blackout curtains and avoiding screens before bed can reduce risk

Artificial light at night dramatically increases heart disease risk by triggering stress responses in the brain that inflame arteries, according to new research presented at the American Heart Association’s Scientific Sessions.

The first-of-its-kind study examined 466 adults with a median age of 55 years. Researchers used brain scans and satellite data to track light exposure levels at participants’ homes. They found a nearly linear relationship between nighttime light and cardiovascular problems.

“The more night-light exposure, the higher the risk,” said Dr. Shady Abohashem, head of PET/CT cardiac imaging trials at Massachusetts General Hospital in Boston. “Even modest increases in night-time light were linked with higher brain and artery stress.”

People exposed to higher artificial light levels showed increased activity in brain regions that activate the body’s fight-or-flight response. This brain activity correlated with greater inflammation in arteries, a key driver of heart disease.

The study tracked participants for up to 10 years. Those with higher nighttime light exposure faced a 35% increased risk of heart attacks within five years and a 22% increased risk over 10 years. After 10 years, 17% of participants had developed major cardiovascular issues.

“This research indicates that light pollution is more than just an annoyance; it could also increase the risk of heart disease,” Abohashem said.

The biological mechanism involves artificial light disrupting natural circadian rhythms. This disruption triggers chronic stress responses in the brain, which then promote inflammation throughout the arterial system. The inflammation raises the likelihood of heart attacks and strokes.

Experts recommend several practical interventions to reduce risk. “People can limit indoor nighttime light, keeping bedrooms dark and avoiding screens such as TVs and personal electronic devices before bed,” researchers advised.

Simple changes include using blackout curtains, dimming outdoor lights, and avoiding bright screens before sleep. Getting regular morning sunlight exposure also helps reset the body’s internal clock.

“Simple light hygiene habits can make a difference,” the study authors noted. Cities can also improve public health by reducing unnecessary outdoor lighting and using motion-sensitive lights.

The findings add to growing evidence that artificial light exposure represents a modifiable cardiovascular risk factor. Previous research shows night owls have a 16% increased risk of heart attack or stroke compared to early risers.

“For clinicians, it’s time to start recognizing light exposure as a modifiable cardiovascular risk factor,” Abohashem said. “The hopeful message here is that this is something we can change.”

Read more: This Common Nighttime Habit May Raise Heart Disease Risk By Up To 35%