Darkness as a Cardiovascular Vital Sign: Nighttime Light May Alter the Heart
A UK Biobank study of 11,071 people found that higher nighttime light exposure (>3 lux) measured by wrist sensors and followed by cardiac MRI three years later is associated with thicker left-ventricular walls, reduced chamber volume, and early signs of impaired heart function, with changes also seen in other heart chambers. The researchers warn that light pollution might contribute to cardiovascular risk and advocate reducing nighttime light exposure (e.g., blackout curtains, warm lighting) as a potential preventive measure, alongside clinicians asking about patients’ sleep environments.