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| My new bedroom never gets properly dark. Street light filters through my blinds; they’re no match for the morning sun, and the problem will only get worse as the days grow longer. I’d been treating this as a mild annoyance until I read two recent studies linking nighttime light exposure to significantly higher cardiovascular risk. I’ve been shopping for a solution, and I think I’ve found one, as you’ll see below.
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Let’s look into it,
Tim Snaith
Newsletter Editor, Healthline
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Written by Tim Snaith
March 11, 2026 • 3 min read |
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| Why you should sleep in total darkness
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| To enjoy the full benefits of a night’s sleep, you won’t need a prescription, a doctor’s visit, or a major lifestyle overhaul. Just a darker room. Two recent studies suggest that the more light you’re exposed to while sleeping, the harder it is on your heart.
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| The first study, published last October, tracked nearly 89,000 adults (average age 62) who wore light sensors on their wrists for a week. Researchers then followed their health records for almost a decade. People who slept in the brightest conditions had up to 56% higher risk of heart failure and 47% higher risk of heart attack compared to those with the darkest bedrooms. These numbers held up even after accounting for exercise, smoking, diet, and sleep duration.
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| A smaller study presented at the American Heart Association’s Scientific Sessions 2025 helps to explain why this pattern emerged. Using brain scans and satellite imagery, researchers found that nighttime light increased brain activity, triggering inflammation in the arteries. Each meaningful increase in light exposure was linked to a 35% higher risk of heart attack over 5 years.
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| The biology is fairly straightforward. When it’s dark, your body produces melatonin, which helps lower blood pressure and your heart rate overnight. Light delays or disrupts the melatonin signal, and your body fails to wind down effectively. Your blood pressure remains elevated, stress hormones linger, and low-grade inflammation affects the walls of your arteries.
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| The first study also found that the increase in the risk of heart failure and coronary artery disease was stronger in women.
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| If your bedroom lets in light, don’t worry — this is one of the simplest cardiovascular risk factors to address. Blackout curtains or shades make the biggest difference. A well-fitted sleep mask works if new curtains aren’t in the budget. You could also swap always-on nightlights for motion-sensing ones. And remember to charge your phone face down, or better yet, leave it in another room.
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| Over to you: Have you tried sleeping with a mask or invested in blackout curtains? Did it make a difference? Email wellnesswire@healthline.com and let us know.
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