Nighttime Light Exposure Linked to Heart Damage

Exposure to artificial light at night may increase the risk of cardiovascular disease, according to a recent study. Researchers from Tulane University and Harvard found that nighttime light exposure is linked to cardiac remodeling, a process that weakens the heart and can lead to heart failure. Light serves as a primary environmental cue that synchronizes the body’s internal 24-hour clock, known as the circadian system, which orchestrates daily patterns of sleep, hormone secretion, metabolism and vascular tone.

How Light Affects the Heart

The study, published in the European Heart Journal, involved over 11,000 participants from the UK Biobank who did not have cardiovascular disease. Each participant wore a light sensor on their wrist for a week to measure their overnight light exposure. Three years later, they underwent a cardiac MRI scan to examine their heart structure and function. The investigators specifically aimed to characterize how nighttime light-driven cardiac remodeling alters ventricular geometry and functional performance, linking the sensor data to later imaging outcomes.

Results showed that those exposed to light levels similar to a supermarket aisle had thickening of the left ventricle wall, one of the heart’s chambers. This thickening reduced the space inside the left ventricle and appeared to decrease the heart muscle’s flexibility during a heartbeat, an early sign of muscle decline. In addition to the left-ventricle changes, the analysis detected modest thickening of the right-ventricle wall and subtle enlargement of the left atrium, suggesting a broader impact on cardiac chambers.

Simple Ways to Reduce Nighttime Light Exposure

The findings suggest that limiting nighttime light exposure could be a way to prevent heart disease. Lu Qi, the study’s lead author and a Distinguished Professor at the Tulane School of Public Health and Tropical Medicine, noted that light pollution has emerged as a new risk factor for heart disease. Because altered lighting disrupts sleep depth and duration, the cumulative stress on the cardiovascular system may be amplified, reinforcing the notion that light pollution constitutes a modifiable risk factor.

For individuals, especially those with atrial fibrillation or heart failure, discussing sleep environments with healthcare providers is key. This includes addressing light pollution, bedroom darkness, night shift work, and screen time after sunset. Clinicians are therefore encouraged to incorporate questions about bedroom illumination, night-shift schedules and evening screen habits into routine cardiovascular risk assessments.

Simple, cost-effective measures to improve sleep and reduce artificial light exposure at night include using warm-colored bedside lighting with a color temperature of 2,000-3,000 Kelvin, turning off computer and smartphone screens 30 to 60 minutes before bed, and installing blackout curtains to block streetlight.