Excessive Light at Night May Change Heart Structure and Function: Study Shows - Video

Too much light at night may be linked to changes in the heart's structure and function, with a new study finding differences among more than 11,000 people.

Published in the European Heart Journal, the study used data from 11,071 UK Biobank participants. Researchers of Tulane University asked participants to wear wrist-based light sensors for seven days to measure their nighttime light exposure. About three years later, participants underwent cardiac MRI scans to assess the heart.

Researchers compared people exposed to more than three lux of light at night with those exposed to almost no nighttime light. The higher-exposure group had thicker walls in the left ventricle, one of the heart’s main pumping chambers. This reduced the space inside the chamber.

The researchers also found signs that the heart muscle was less able to relax and change shape during a heartbeat. Changes were also observed in the right ventricles and the left atrium, suggesting that nighttime light exposure may be associated with broader changes in cardiac structure and function.

These structural changes are known as cardiac remodelling. They can occur when the heart adapts to prolonged stress or injury and, over time, may contribute to impaired heart function.

However, the study was observational, meaning it can identify an association but cannot prove that nighttime light directly causes heart damage. Other factors linked to both light exposure and cardiovascular health may also contribute to the findings.

Researchers said the results add to previous evidence connecting nighttime light exposure with cardiovascular disease and suggest that reducing exposure could become part of heart-health strategies.

Experts recommend keeping bedrooms as dark as possible, using warmer and dimmer lights after sunset, limiting bright screen exposure at night and covering unnecessary electronic lights. Larger studies are needed to determine whether reducing nighttime light can directly improve cardiovascular health.

REFERENCE: Jin Dai, Wen Dai, et al.; Nighttime light exposure and cardiac structure and function; European Heart Journal; 2026; DOI; 10.1093/eurheartj/ehag563