A study of over 11,000 people suggests that exposure to light at night may lead to structural and functional changes in the heart.

A study published September 9 in the European Heart Journal found that nighttime light exposure is associated with potentially harmful changes to the heart. Researchers led by Professor Lu Qi of Tulane University analyzed data from 11,071 participants in the UK Biobank to examine the link between light levels and cardiac health.

Study Methodology and Findings

Participants wore wrist-mounted light sensors for seven days to measure nighttime light exposure. Three years later, researchers conducted cardiac MRI scans to assess heart structure and function. The study compared individuals exposed to nighttime light levels above three lux against those exposed to almost no light. Results indicated that higher nighttime light exposure was linked to thickening of the left ventricle wall, which reduced the chamber's internal space. Scans also showed reduced heart muscle flexibility and changes in the right ventricles and left atria. Professor Qi noted that these findings suggest cardiac remodeling, a process typically seen in response to chronic stress or injury that can eventually weaken the heart.

Clinical and Public Health Implications

An accompanying editorial by Professor Thomas Münzel and colleagues suggests that clinicians should consider a patient's sleep environment, including bedroom darkness and screen use, when managing heart conditions like heart failure or atrial fibrillation. The authors recommend simple interventions such as blackout curtains and warm-colored lighting. From a public health perspective, the editorial highlights light pollution as an environmental hazard that cities can address through shielded fixtures and dimming streetlights. The authors argue that darkness should be recognized as a vital sign for cardiovascular health.