New Delhi: Falling asleep with the television playing in the background can appear to have a comforting effect on the body; however, new research suggests
that it could be quietly putting your heart at risk. As per a large international study, regular exposure to light while sleeping is linked with a heightened risk of heart disease, even among people who sleep well.
The findings come from a collaboration between researchers from Australia and the US, who followed 90,000 adults in the UK for nine years. Participants were given light sensors to measure how much light they were exposed to at night. This helped researchers move beyond self-reported habits and capture the real state of sleep habits among people.
During the course of the study, researchers tracked new diagnoses of heart ailments, from heart attacks to heart failure, from stroke to coronary artery disease. The pattern that appeared was concerning and consistent – people exposed to too much light at night were more prone to five heart problems, regardless of how long they slept or the quality of their sleep.
Those with the highest night-time light exposure faced the greatest risks. Compared with participants who slept in near-total darkness, they were 56 per cent more likely to develop heart failure and 47 per cent more likely to suffer a heart attack. The risk of coronary artery disease rose by 32 per cent, while stroke risk increased by 30 per cent. Women who appeared vulnerable with high rates of coronary artery disease linked to night-time light exposure than men.
Writing in JAMA Network Open, the researchers said disruption of the body’s circadian rhythm — the internal clock that regulates sleep, hormones, and metabolism — was the most likely explanation. Artificial light at night interferes with this system, pushing the body into a state of physiological imbalance that may, over time, strain the cardiovascular system.
“Night light exposure was a significant risk factor for developing cardiovascular disease in adults over 40,” the authors noted, adding that reducing light at night could be a simple, low-cost prevention strategy.
Professor Frank Scheer, a neuroscientist at Brigham and Women’s Hospital in Boston and one of the study’s authors, said the findings should prompt doctors to ask patients about their sleep environment — not just how many hours they spend in bed. “There’s really no downside to keeping the bedroom dark,” he said. “A very dim light for safety is fine, but bright light has no benefit during sleep.”
He explained that light levels below five lux — roughly equivalent to the glow of a few candles — are unlikely to disrupt the circadian system, while still allowing people to see their surroundings.
Dr Daniel Windred, a sleep health researcher at Flinders University in Australia, said the strength of the association surprised the team. “We expected an effect, but seeing nearly a 60 per cent increase in heart failure risk places night-time light alongside established cardiovascular risk factors,” he said.
The findings land against a backdrop of widespread sleep problems. In the UK, around one in six adults reports insomnia, yet most never seek help. While waking during the night does not automatically signal a sleep disorder, chronic sleep disruption — compounded by light exposure — can take a long-term toll, increasing the risk of heart disease, diabetes, and obesity.
For experts, the message is straightforward: when it comes to sleep, darker may be healthier — and your heart could benefit from switching the lights off.
