It turns out that your annoying friend who insists on closing all of the window blinds and covering all of the glowing electronics in a bedroom in order to sleep in total darkness is onto something. New research bolsters the well-established theory linking nighttime light to adverse health impacts.

A preliminary analysis set to be presented at the American Heart Association’s Scientific Sessions 2025, starting Friday, suggests that the state of darkness while we sleep plays a crucial role in our overall health. The results link more artificial light at night, also known as artificial nighttime light pollution, with higher brain stress signals, inflamed blood vessels, and greater risk of heart disease —a broad term for different heart problems.

“We know that environmental factors, suc

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