Nighttime light exposure may be linked with top killer disease worldwide – CTV
October 28, 2025
Turning off the lights at night has long been known to support restful sleep, but new research suggests it may have another significant benefit. Sleeping in total darkness may lower the risk for cardiovascular disease, the top cause of death worldwide.
People who slept in the brightest conditions — similar to having overhead bedroom lights on —had a 56% greater risk of developing heart failure. Those who slept under such intense light also had a 32% higher risk of coronary artery disease and a 28% higher risk of stroke.
Wrist wearables tracked the study participants’ exposure to light intensity between 12:30 a.m. and 6 a.m., according to Dr. Daniel Windred, co-first author of the study published Thursday in the journal JAMA Network Open.
“One limitation is that we do not know the sources of personal light exposure, only the intensity,” said Windred, a research associate at Flinders University’s College of Medicine and Public Health in Australia. “Understanding typical sources of night light exposure might allow for more informed recommendations beyond ‘avoid bright light at night.’”
