New research sheds light on how artificial brightness could raise your cardiovascular stakes
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Even when taking into account exercise, diet, sleep habits and genetics, higher nighttime light exposure was linked with increased heart and vascular issues.
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Researchers tracked nearly 89,000 adults for up to 9.5 years using wrist-worn light sensors to see how light at night fits into heart health.
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People in the highest night-light exposure group had significantly higher risks of coronary artery disease, heart attack, heart failure, atrial fibrillation and stroke.
We know things like diet, smoking, exercise and sleep matter for heart health but what about the lights in your bedroom?
A new study led by Flinders University in Australia found that being exposed to brighter light at night may be an independent risk factor for serious heart- and blood-vessel related problems.
The researchers suggest that, beyond what you already know about lifestyle, simply living and sleeping in a brighter-than-dark environment may be doing its own damage.
This is 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, researcher Dr. Daniel Windred said in a news release.
Disrupting your bodys internal circadian clock by repeatedly exposing yourself to bright light at night, when it would typically be dark otherwise, will put you at a higher risk of developing dangerous heart issues.
The study
To get at this question, the team used data from the UK Biobank cohort: 88,905 adults aged over 40 who wore wrist-mounted light sensors for about a week.
The sensors recorded personal light exposure both during the day and at night (defined roughly from 12:30 a.m. to 6:00 a.m.). The researchers then followed these participants for up to 9.5 years (June 2013 to November 2022) to see who developed cardiovascular issues such as coronary artery disease, heart attack (myocardial infarction), heart failure, atrial fibrillation or stroke.
They adjusted for many potential confounders: age, sex, ethnicity, household income, education, smoking, alcohol consumption, diet score, sleep, physical activity and even genetic risk of cardiovascular disease.
The results
The researchers found that the more light people were exposed to while sleeping, the higher their odds of developing heart problems later on. Those in the brightest nighttime-light group were noticeably more likely to experience major cardiovascular conditions even after accounting for other health factors like exercise, diet, and genetics.
Compared to people who slept in darker environments, those with the most night-time light exposure had about:
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30% higher risk of developing coronary artery disease, which can block blood flow to the heart
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50% higher risk of a heart attack or heart failure, both of which can be life-threatening
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30% higher risk of atrial fibrillation, a condition that causes irregular heartbeat
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25% higher risk of stroke, which occurs when blood flow to the brain is disrupted
Interestingly, the connection between night light and heart disease appeared stronger in women and younger adults, suggesting that some groups may be more sensitive to light exposure during sleep.
Even when researchers controlled for sleep duration and quality, physical activity, and family history, the link remained meaning light at night itself may play a role.
Keeping the lights low
The researchers emphasized that even small habits can make a difference when it comes to our sleeping habits and risk of heart concerns.
Thankfully, we do have some control over our exposure to light at night, Dr. Windred said. By using blackout curtains, dimming lights, and avoiding screens before bed, we can help to reduce the health risks associated with light at night.
Everyday habits, like scrolling on your phone in bed or falling asleep with the TV on or bedroom lights on, can expose you to potentially harmful levels of light, Associate Professor Andrew Phillips said in the news release.
Were not talking about extreme cases, even low levels of indoor light can interfere with your bodys natural rhythm.
Posted: 2025-11-05 02:28:16
