It Turns Out Your Bedroom Light Could Be Bad For Your Heart

Sleep and heart health seem to be linked, with one paper suggesting that 11 extra minutes of kip a night could lower your heart attack risk.

Obstructive sleep apnoea, meanwhile, is associated with higher blood pressure, and insomnia seems connected to worse cardiovascular outcomes too.

And according to a new paper published in the European Heart Journal, even the lighting setup you have while snoozing might be consequential.

This research involved over 11,000 participants who made their health data available to scientists through the UK Biobank.

Those involved in the research wore a light sensor wristband for a week to measure how bright their surroundings were at night.

And three years after that, researchers checked their hearts with an MRI scan.

Compared to those who were exposed to dark conditions at night, people whose environment was more than three lux bright (a dim light level that nonetheless seems to suppress sleep hormone melatonin) saw a thickening of the walls in their heart’s left ventricle.

It also looked like their hearts were less able to bend during a heartbeat, an early indicator of cardiovascular issues.

Study author Professor Qi said that this “shows that exposure to higher levels of light at nighttime is linked to cardiac remodelling. This is where the structure and function of the heart changes and we typically see it in response to chronic stress or injury to the heart.

“It’s our body’s way of adapting to that stress, but ultimately it weakens the heart and can lead to heart failure.”

He suggested this could mean light pollution is “a new risk factor for cardiovascular disease”, and said we should start considering darker environments as a possible heart disease prevention strategy.

In an editorial related to the paper’s release, Professor Thomas Münzel, who was not involved in the study, said that clinicians working with patients who have heart issues should start asking them about their sleeping conditions.

Questions could include how dark their room is, how much screen time they get after bedtime, and whether they work the night shift (a factor already linked to increased heart disease risk).

“The advice is simple and inexpensive: blackout curtains, warm-coloured bedside lighting, and covering the small standby LEDs on household electronics,” he said.

And on a policy level, we should start to tackle light pollution, he added.

“Ultimately, this study is more than an interesting observation. It provides a crucial link between what satellites already show us, i.e., a planet glowing ever brighter at night, and the clinical reality unfolding inside our chests: hearts that are becoming stiffer, weaker, and less efficient.

“The relationship is biologically coherent, the effect sizes are clinically meaningful, and the dose-response is unambiguous: more light, worse outcomes. The takeaway is clear: darkness deserves recognition as a vital sign, as essential to cardiovascular health as blood pressure control and clean air.”