Adults exposed to more light during their nightly rest period had slightly thicker heart muscle walls and signs of weaker heart muscle function on MRI scans about three years later, according to a study of 11,071 UK adults published Sept. 9 in the European Heart Journal. The study was observational, which means it found an association and did not prove that light at night causes heart changes.
The researchers focused on light above 3 lux, a level at which experimental research suggests the body's nighttime release of melatonin can be suppressed. For comparison, a very dark night outdoors can measure below 1 lux, while indoor lighting is considerably brighter.
