# Your bedroom light may be straining your heart

> A new study scanned the hearts of people who sleep with the lights on, and found walls that had already thickened.
- Title: Your bedroom light may be straining your heart · TIME
- Summary: A new study scanned the hearts of people who sleep with the lights on, and found walls that had already thickened. Make the bedroom as dark as you can…
- Keywords: sleep, heart health, light exposure, cardiology, research, bedroom, light, may, straining, heart, TIME
- Source: TIME — https://time.com/article/2026/09/11/light-exposure-at-night-is-linked-to-heart-changes
- Author: Veronique Greenwood
- Published: 2026-09-11T17:19:36.492+00:00
- Read time: 1 min
- Topics: sleep, heart health, light exposure, cardiology, research
## Night used to be dark
For almost all of human history, sunset meant total blackness. Now a hall light, a streetlamp, or a TV two rooms away keeps most of us in a permanent dim glow.

> For most of human history, night has been dark. Very, very dark
## A pattern keeps showing up
Light at night already tracks with higher rates of diabetes, obesity, and hypertension. Last year researchers tied it to heart failure and other cardiovascular problems over a decade.
## Now the heart itself
A team publishing in the European Heart Journal on September 9 reports that people exposed to light at night have structural changes in their hearts, signs the organ is working harder than it should.
## Sensors, not memories
Researchers used UK Biobank fitness monitors with built-in light sensors, worn for a week. Most earlier studies just asked people how bright their bedrooms were.

> That's very unique, because most previous studies have used self-reported light exposure
## Three candles is enough
People sleeping under at least 3 lux, roughly three candles held three feet away, had thicker heart walls and weaker pumping on MRI. Not disease yet, but what comes before it.
## Just turn it off
The link is correlational, and nobody knows if the culprit was a tablet, a TV, or the hallway. Still, darkness is free: blackout curtains, lights off, an eye mask.

> Draw an eye mask over your eyes, and know that it could be helping your heart.
## Key takeaway

Make the bedroom as dark as you can. Blackout curtains, hall light off, eye mask on, and your heart may thank you for it.