Sleeping with lights on could be more harmful than previously thought. New research shows that increased exposure to artificial light at night may raise the risk of developing several major cardiovascular conditions. The findings, based on data from nearly 89,000 individuals, highlight how nighttime brightness may be a significant contributor to heart health complications.
The study indicates that exposure to light at night disrupts the body’s natural circadian rhythm the internal biological clock that regulates sleep-wake cycles. This disruption is increasingly being recognized as a risk factor for a range of adverse health outcomes, particularly those affecting the cardiovascular system.
Researchers analyzed over 13 million hours of personal light exposure data, gathered through wrist-worn sensors that tracked participants’ light environments over a one-week period. Participants were then monitored for the development of cardiovascular diseases such as coronary artery disease, heart attacks, heart failure, atrial fibrillation, and stroke.
Notably, individuals who were exposed to the brightest levels of nighttime light had significantly higher risks of developing these conditions compared to those who slept in darker environments. These associations remained strong even after accounting for other known cardiovascular risk factors, including physical activity, smoking, alcohol consumption, dietary habits, sleep duration, socioeconomic status, and genetic predisposition.
The study also found that women and younger individuals appeared to be more vulnerable to the negative effects of light exposure at night. For women, the associations were particularly strong for heart failure and coronary artery disease. Among younger participants, there was an increased risk of heart failure and atrial fibrillation.
These findings suggest that minimizing exposure to artificial light during nighttime hours could serve as an additional preventive strategy in the fight against heart disease. Artificial light at night whether from screens, lamps, or streetlights can interfere with melatonin production, sleep quality, and hormonal balance, all of which are essential for maintaining cardiovascular health.
By disrupting natural circadian rhythms, light at night may trigger metabolic and vascular changes that elevate cardiovascular risk. As urban environments become increasingly illuminated, understanding and mitigating this risk becomes more urgent.
Avoiding unnecessary light in the bedroom, using blackout curtains, and limiting screen use before bed may help reduce exposure and support better heart health. While further peer-reviewed studies are needed, the evidence increasingly supports the idea that darkness during sleep is not just important for rest but also for protecting the heart.