"Nighttime Light Linked to 50% Heart Attack Increase"

"Nighttime Light Linked to 50% Heart Attack Increase"

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A Common Bedroom Feature Could Increase Heart Attack Risk by 50%

If you’ve hung blackout curtains or plugged in a nightlight, your choice could have a profound effect on your health, new research shows.

An October 2025 study by a team of cell biology researchers from Australia, England, and the USA tracked nearly 90,000 participants’ nighttime light exposure for one week between 2013 and 2016, then tracked their health outcomes over the following eight years. Their findings revealed a strong link between artificial light at night (LAN) and an increased risk of cardiovascular disease (CVD).

They sum up their takeaways for the sample, all of whom were age 40 or older: “Exposure to brighter light at night was associated with higher risks of coronary artery disease, myocardial infarction, heart failure, atrial fibrillation, and stroke, independent of established cardiovascular risk factors.”

To break it down, participants exposed to the brightest nighttime light saw up to a 50% higher chance of having a heart attack compared with those living in darker environments. They were also more likely to develop coronary heart disease, stroke, atrial fibrillation, and heart failure. “When the same individuals were exposed to room light (about 100 lux) compared with dim light (less than 3 lux) during their sleep period, they exhibited elevated heart rate, disrupted deep sleep, and worse insulin sensitivity,” the study authors noted.

To illustrate this, a typical office or living room light might fall within 100 and 500 lux, while 3 lux is nightlight-level.

As the researchers noted, these findings held true even after accounting for factors such as sleep timing, sleep duration, sleep efficiency, physical activity, and seasonal daylight variation. This suggests that the health effects of artificial light are not merely consequences of poor or shortened sleep—instead, light exposure during sleep appeared to exist as a risk factor of its own.

One way that nighttime light could cause heightened heart risk involves the disruption of melatonin production. Normally, melatonin levels rise in the evening, signaling the body to prepare for sleep and helping maintain the circadian rhythm. Exposure to artificial light near bedtime—whether from indoor lighting or outdoor light pollution—can delay or reduce melatonin secretion, disturbing these natural rhythms.

The researchers observed that some groups appeared especially vulnerable to melatonin suppression. Women and younger participants were more sensitive to the increased heart risk. In fact, high levels of nighttime light exposure reduced the usual protective effect of being female against heart failure. “Just as all light is not uniform, neither are we as individuals. Indeed, the light intensity needed to significantly suppress evening melatonin secretion is higher following greater daytime light exposure, and can differ by several 10-fold across individuals,” the team noted.

So, as you tuck yourself in, consider that total darkness may offer the greatest health benefits. Wearing a sleep mask or drawing the curtains tight could offer bigger benefit than a peaceful night’s sleep.

Conclusion

As we learn more about the impact of nighttime light on our health, it becomes increasingly clear that our bedroom environment plays a significant role in our overall well-being. By making simple adjustments, such as keeping the bedroom dark and free from artificial light, we can potentially reduce our risk of heart disease and other cardiovascular issues. Let’s prioritize creating a sleep-friendly environment to support our health and well-being.

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Hi, I’m Ciro Irmici, an entrepreneur and investor from San Severo, Italy. My passions range from investments (stocks, crypto, dividends) to automation and creating businesses that help people. I believe in building things that matter, like a gym for all and a theatre for people to enjoy music. I love learning and sharing what I learn: how to create eBooks, audiobooks, and other digital products. I’m also deeply into fitness (gym, running, jump rope) and creativity (painting, music, design). My ultimate goal? To reach financial freedom and help others achieve their dreams.

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