Nighttime Light Exposure May Weaken the Heart, Raise CVD Risk

Even low levels of nighttime light exposure were linked to structural and functional changes in the heart, along with a higher long-term risk of heart failure, atrial fibrillation (AF), myocardial infarction (MI), stroke, and cardiovascular (CV) mortality, according to a study published in the European Heart Journal.¹

“Previous observational studies have linked nighttime light exposure with a higher risk of cardiovascular diseases, but little is known about the related cardiac structure and functional changes,” said lead author Lu Qi, MD, PhD, HCA Regents Distinguished Chair and professor at Tulane, in a statement.² “We carried out this research to find out what happens to the heart over time when people are exposed to too much light at nighttime.”

Cardiac Remodeling Tracked to Light Exposure

The analysis included 11,017 UK Biobank participants who wore a wrist accelerometer with an integrated light sensor for 7 days between 2013 and 2015 and later underwent CV MRI a median of 3.1 years after baseline. Researchers compared participants exposed to more than 3 lux of nighttime light, roughly equivalent to a dimly lit phone screen or a hallway light, with those who had no measurable nighttime light exposure.

After adjustment for sociodemographic, lifestyle, health, and environmental factors, participants with high nighttime light exposure had 2.4% greater left ventricular (LV) mass indexed to height, 1.5% greater mean wall thickness, and 1.9% lower myocardial contraction fraction than those with no exposure. They also had reduced myocardial strain across circumferential, radial, and longitudinal measures, indicating impaired heart muscle deformation. Similar adverse associations were observed for right ventricular volumes and left atrial size and function, and all associations followed a linear dose-response pattern.

Sleep Duration Explains Part of the Association

The study found that shorter sleep duration accounted for 24% to 49% of the associations between nighttime light exposure and adverse cardiac findings, with the largest contributions seen for relative wall mass (49%), maximal wall thickness (41%), and interventricular septal thickness (39%). Over 8 to 10 years of follow-up, participants with high nighttime light exposure had a 29% higher risk of heart failure, 15% higher risk of AF, 24% higher risk of MI, 33% higher risk of stroke, and 26% higher risk of CV mortality compared with those unexposed.

The findings build on a broader body of evidence connecting circadian disruption to cardiometabolic disease. An American Heart Association (AHA) scientific statement published in Circulation last year concluded that disruptions to circadian rhythms—driven by factors including irregular sleep, shift work, and nighttime light exposure—are strongly associated with obesity, type 2 diabetes, hypertension, and CV disease, and it identified nighttime light avoidance as one of several modifiable behavioral targets for reducing cardiometabolic risk.³

Managed Care Implications

Because nighttime light exposure is largely within an individual's control, the authors framed it as a modifiable target that could complement existing approaches to CV risk reduction.¹ They noted that further research is needed to determine whether interventions specifically aimed at reducing nighttime light exposure translate into fewer cardiac events but said the consistency of the dose-response pattern across multiple heart chambers strengthens the case for considering light exposure as an independent circadian risk factor for cardiovascular disease.

“Light pollution has emerged as a new risk factor for cardiovascular disease,” said Qi in a statement.² “Our findings, together with evidence from other studies, suggest that a reduction in nighttime light exposure should be considered as one of the potential strategies for preventing heart disease by clinicians and policymakers.”

References

1. Dai J, Dai W, Heianza Y, Qi L. Nighttime light exposure and cardiac structure and function. Eur Heart J. Published online September 9, 2026. doi:10.1093/eurheartj/ehag563
2. Even low levels of nighttime light exposure may weaken the heart, increase the risk of cardiovascular disease. News release. Tulane University. September 9, 2026. Accessed September 10, 2026. https://www.eurekalert.org/news-releases/1143376
3. Knutson KL, Johnson DA, Dixon DD, et al. Role of circadian health in cardiometabolic health and disease risk: a scientific statement from the American Heart Association. Circulation. Published online October 28, 2025. doi:10.1161/CIR.0000000000001388