Nighttime light alters heart structure

Objective wrist‑worn light measurements and cardiac MRI in 11,000 UK Biobank participants show that regular nighttime light above ~3 lux is associated with slight thickening of the left ventricular wall and smaller pump volume, partially mediated by reduced sleep duration. The effect size is small on average but could raise risk for people with preexisting cardiovascular disease and points to light pollution as a modifiable environmental health factor. — If replicated and causal, urban and consumer lighting standards and sleep‑health policy would become matters of cardiovascular prevention and urban design, not just astronomy and aesthetics.