It seems that that friend of yours who insists on shutting all the window blinds and covering up glowing electronics to achieve complete darkness while sleeping actually has a point. Recent research supports the long-standing theory connecting nighttime light exposure to negative health outcomes.
A preliminary analysis, which will be discussed at the American Heart Association’s Scientific Sessions 2025 starting Friday, indicates that the darkness we experience while sleeping is vital for our overall well-being. The findings show that increased exposure to artificial light at night, often referred to as nighttime light pollution, is associated with heightened brain stress signals, inflamed blood vessels, and an elevated risk of heart disease—a term that encompasses various heart-related issues.
According to Shady Abohashem, who leads cardiac PET/CT imaging trials at Massachusetts General Hospital and is a senior author of the forthcoming study, “We recognize that environmental elements like air and noise pollution contribute to heart disease by affecting our nerves and blood vessels through stress. Light pollution is prevalent, yet we know relatively little about its impact on heart health,” as he noted in a statement from the American Heart Association.
Artificial Light at Home
In this observational study, Abohashem and his team analyzed health data from 466 adults who had undergone identical Positron Emission Tomography/Computed Tomography (PET/CT) scans at Massachusetts General Hospital between 2005 and 2008 to identify brain stress signals and artery inflammation. They also considered the participants’ exposure to artificial nighttime brightness at home, referring to the 2016 New World Atlas of Artificial Night Sky Brightness.
The results revealed that individuals exposed to higher levels of nighttime artificial light displayed increased brain stress activity and inflammation in blood vessels, as well as a heightened risk of heart disease. Not surprisingly, those living in areas with additional stressors—like heavy traffic noise or lower income—had an even greater risk of heart problems. By the end of 2018, 17% of the participants had suffered significant heart issues.
The study found a nearly straightforward link between nighttime light exposure and heart disease: more light exposure resulted in a higher risk. Even slight increases in nighttime light were tied to raised brain and artery stress, as Abohashem pointed out. This correlation persisted even after accounting for known heart risk factors and other environmental stresses.
“When the brain detects stress, it activates signals that can incite an immune response and inflame the blood vessels,” he elaborated. “Over time, this process may lead to arterial hardening, raising the chances of a heart attack or stroke.”
Reducing Light Exposure
What can we do in light of this? Abohashem suggests cities consider reducing unnecessary outdoor lighting, while individuals could cut down on indoor light before bedtime, including screens—so that means no more late-night TikTok scrolling.
“We understand that excessive exposure to artificial light at night can be detrimental to your health, particularly in increasing heart disease risk. But we have been uncertain about how this harm manifests,” said Julio Fernandez-Mendoza, director of behavioral sleep medicine at Pennsylvania State University College of Medicine, who was not associated with the study. “This research has explored one potential mechanism, specifically how our brains react to stress, which appears to play a significant role in linking nighttime light with heart disease.”
However, there are limitations to the research. The participants were sourced from a single hospital system, which might affect the diversity of the group, making the findings possibly less representative of the general population. Additionally, due to the observational nature of the study, it cannot confirm a causal relationship.
“We aim to broaden this research to larger, more diverse groups, test interventions to reduce nighttime light exposure, and investigate how minimizing light may improve heart health,” Abohashem concluded.
