A large-scale study presented this week at the American Heart Association sessions suggests a concerning link between exposure too artificial light during sleep and an increased risk of cardiovascular disease. Researchers at Massachusetts General Hospital in Boston followed nearly 466,000 adults for a decade, finding that even moderate nighttime light exposure correlated with a significantly higher chance of heart attack and stroke. While the research is still awaiting peer review, the findings add to a growing body of evidence highlighting the importance of darkness for optimal health and sleep quality.
Exposure to light while sleeping may significantly increase the risk of heart problems, according to new research. The study, conducted by researchers at Massachusetts General Hospital in Boston, found that even moderate levels of artificial light at night can contribute to brain stress and inflammation of arteries, potentially leading to heart attack or stroke.
Researchers discovered a direct correlation between nighttime light exposure and the future development of cardiovascular disease. The findings highlight the importance of sleep hygiene for long-term heart health.
For every standard deviation increase in light exposure, the likelihood of experiencing a heart attack rose by 35% within the next five years, and by 22% over the following decade.
Over a 10-year follow-up period, 17% of the study participants developed significant cardiovascular issues. This underscores the potential long-term consequences of disrupted sleep environments.
The study also indicated that individuals living in areas with high levels of noise pollution, near major roadways, or in disadvantaged neighborhoods were more susceptible to the negative effects of nighttime light. These environmental factors may compound the risks associated with light exposure.
The research involved 466,000 adults, none of whom had pre-existing heart conditions or cancer, and who underwent brain scans at Massachusetts General Hospital in Boston between 2005 and 2008.
Researchers measured light levels in participants’ homes during sleep using data collected from satellites.
The study was presented at the American Heart Association sessions in 2025 and has not yet been published in a peer-reviewed scientific journal.
“This study confirms that sleeping in darkness is best for health,” said Jonathan Cedernaes, a sleep expert at Uppsala University in Sweden. “Research on both animals and humans has shown that nighttime light disrupts neurological and physiological systems, and impacts metabolism and inflammation.”
According to a report by Headline, the research reinforces the idea that complete darkness is optimal for achieving higher quality sleep.
Experts recommend covering windows, sealing gaps, and wearing a sleep mask to create an ideal sleep environment that promotes relaxation.
