A Bedroom That Is Not Quite Dark Is Linked to a Thicker, Stiffer Heart, in the First Study to Measure Both
Eleven thousand people wore a light sensor for a week. Three years later, those who slept in more than three lux, a very dim room, had thicker left ventricles and muscle that flexed less. The differences are small. Cardiologists still care.
Sep 12, 2026


