Nighttime Light Exposure Linked to Heart Disease

Three illuminated heart shapes created with sparklers over a dark road at night. Photo: Johannes Plenio/Pexels

Light serves as a vital cue for the body’s internal 24-hour clock and its circadian rhythms, which oversee biological functions like sleep, wakefulness, digestion, and hormone release. Disrupting these rhythms can negatively impact cardiovascular health, and research has shown that nighttime artificial light exposure raises the risk of cardiovascular disease.

Researchers from Tulane University and Harvard found that nighttime exposure to artificial light is associated with cardiac remodeling, which can weaken the heart and potentially lead to heart failure. Lu Qi, the lead author, explained that people exposed to high levels of light had thickening of the wall of their left ventricles.

The researchers enrolled over 11,000 participants in 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 and underwent a cardiac electromagnetic imaging (MRI) scan three years later.

Participants exposed to light levels equivalent to that of a supermarket aisle had thickening of the wall of their left ventricle compared to those exposed to low levels of light or no light. This thickening reduced the space inside the left ventricle and appeared to reduce the heart muscle’s ability to flex during a heartbeat.

Qi noted that light pollution has emerged as a new risk factor for heart disease. The findings suggest that limiting nighttime light exposure is a possible way to prevent heart disease. Doctors caring for patients with atrial fibrillation or heart failure should discuss the sleep environment with their patients, including the issue of light pollution.

Some simple ways to improve sleep and reduce nighttime exposure to artificial light include using warm-colored bedside lighting, turning off computer and smartphone screens before bed, and installing blackout curtains to block streetlight.

The study and an accompanying editorial are published in the European Heart Journal. As they continue to explore the link between light exposure and heart health, it is possible that limiting nighttime light exposure could become a key component of cardiovascular disease prevention strategies. The European Heart Journal publication provides further insight into the research and its implications for heart health.