WASHINGTON (dpa-AFX) - People who slept in brightly lit rooms had a much higher risk of heart problems, according to a recent study published in JAMA Network Open.
Researchers studied 88,905 people from the UK Biobank who wore wrist sensors that tracked their light exposure for a week between 2013 and 2016. The data of about 13 million hours of light recordings was linked with their health records over the next 9.5 years, until late 2022. The sensors measured how much light participants were exposed to between 12:30 a.m. and 6 a.m., the key hours for sleep.
The study found that exposure to bright light during these hours disrupted the body's circadian rhythm that controls heart rate, blood pressure, and hormone release, causing 56 percent more chance to develop heart failure, 32 percent more chance to get coronary artery disease, and 28 percent more chance to have a stroke.
The researchers explained that blood pressure generally drops during sleep, and stress hormones rise in the morning. But bright light at night confuses the body, keeping blood pressure high and throwing off hormone timing. It also disturbs the balance between the 'fight or flight' system and the 'rest and digest' system.
In short, this raises heart rate, inflammation, and blood clotting. Over time, it can lead to artery damage (atherosclerosis), heart attacks, and irregular heartbeats that increase stroke risk.
The study also found that women were more affected by nighttime light than men, especially when it came to heart failure and coronary artery disease, possibly because women's body clocks are more sensitive to light.
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