Study Links Nighttime Light Exposure to Cardiac Remodeling

A new analysis of data from the UK Biobank indicates that exposure to modest levels of light during sleep can alter heart muscle structure and impair its pumping efficiency. Participants who slept in rooms illuminated above 3 lux – roughly the brightness of moonlight leaking under a door – showed thickening of the left-ventricle wall and decreased flexibility of the heart muscle three years later, signs of early cardiac remodeling.

The study, published in the European Heart Journal, tracked more than 11,000 adults without prior cardiovascular disease using wrist-worn sensors for a week to record nighttime light levels. Follow-up cardiovascular magnetic resonance scans assessed heart morphology and function.

"Light pollution has emerged as a new risk factor for cardiovascular disease," said Dr. Lu Qi, senior author and professor at Tulane University.

"Our findings, together with evidence from other studies, suggest that reduction of nighttime light exposure should be considered as one of the potential strategies for preventing heart disease," Qi added.

Researchers estimated that 24-49% of the observed cardiac changes could be linked to shorter sleep duration (under five or six hours) caused by night-time light, while the remainder may involve stress-related mechanisms such as blood-pressure fluctuations.

Experts not involved in the research cautioned that a single week of wrist-sensor data may not accurately reflect ocular light exposure and that the observational design cannot prove causality. Further investigations are needed to confirm the relationship.

Public health recommendations include keeping bedrooms at or below 1 lux, using blackout curtains or masks, and selecting low-intensity, warm-colored night-lights if needed.