Bright light risks: Scrolling your phone or keeping the lights on late could be doing more than stealing sleep. Adults over 40 who were exposed to bright light at night had a 56% higher risk of heart failure, according to a large study led by researchers at Flinders University in Australia and published in JAMA Network Open.
The team analysed 13 million+ hours of light exposure from wrist-worn sensors on nearly 89,000 UK adults, tracking participants for more than nine years. Night-time light exposure was also associated with a 47% higher risk of heart attack, 32% higher risk of coronary artery disease, and 28% higher risk of stroke.
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“Night light exposure was a significant risk factor for developing cardiovascular diseases among adults older than 40 years,” the authors wrote. Lead author Daniel Windred called it “the first large-scale study to show that simply being exposed to light at night is a strong and independent risk factor for heart disease,” adding that regularly disrupting the body’s circadian clock with bright light may elevate the risk of dangerous heart problems.
The analysis suggested women and younger participants were especially vulnerable. Senior co-author Sean Cain noted that women exposed to high levels of night light showed heart failure risks comparable to men, an unusual pattern given women’s typical partial protection against heart disease. The team suggested simple steps to cut exposure, such as using blackout curtains, dimming household lights in the evening, and avoiding screens before bed.
