Midazolam is a medicine that helps people relax or fall asleep before surgery. It works so well that many patients don’t remember the procedure afterward. But a new study shows that this commonly used drug might have a hidden danger—especially when it’s given at night.
Researchers from the University of Colorado Anschutz Medical Campus studied over 1.7 million patient records. All of these patients had received midazolam before surgery. Most were fine, but more than 16,000 showed signs of heart injury after the procedure.
When the scientists looked closer, they found something surprising: surgeries done at night had a higher risk of heart damage, especially in patients who were otherwise healthy.
This led the team to ask an important question: Why would the time of surgery matter?
The answer may lie in a special gene called PER2. This gene helps protect the heart and is part of the body’s internal clock—our circadian rhythm. This rhythm helps our body know when it’s day or night, and it controls many body functions like sleep, hormone release, and even how organs respond to stress.
The researchers ran experiments with mice and found that midazolam seemed to lower the levels of the PER2 gene—but only at night. This is concerning because PER2 naturally drops at night anyway, so when midazolam reduces it even more, the heart may be left without enough protection. That could explain why more heart problems happen when the drug is given during nighttime surgeries.
Midazolam works by increasing a calming chemical in the brain called GABA. This helps people feel relaxed and sleepy, which is why it’s used before surgeries and medical procedures. But this calming effect might also influence the heart’s natural defense system—especially when the body is already in its low-protection nighttime state.
This discovery shows that it’s not just the type of medicine that matters—it’s also when it’s given. This idea is part of a growing area of research called chronomedicine, which studies how timing affects how the body responds to treatments.
Some blood pressure medications, for example, are known to work better if taken at night. Now, this study suggests we may need to think more carefully about the timing of sedatives like midazolam too.
For most people, midazolam is still a safe and helpful medicine. But this study, led by Dr. Tobias Eckle and published in Frontiers in Cardiovascular Medicine, shows that even commonly used drugs can have risks we didn’t expect—especially when timing is involved.
This research is a powerful reminder that small details, like what time a surgery takes place, can make a big difference in patient safety. As doctors and hospitals learn more from studies like this, they may adjust how and when medications are used to better protect patients’ health.
If you care about heart health, please read studies that vitamin K helps cut heart disease risk by a third, and a year of exercise reversed worrisome heart failure.
For more health information, please see recent studies about supplements that could help prevent heart disease, stroke, and results showing this food ingredient may strongly increase heart disease death risk.
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