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Heart Surgery Is Safer If It's Scheduled In The Afternoon, New Study Suggests


Katy Evans

Katy is Managing Editor at IFLScience where she oversees editorial content from News articles to Features, and even occasionally writes some.

Managing Editor

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A new study has suggested that open heart surgery is more successful when performed in the afternoon rather than the morning. Now, before you go canceling your scheduled morning surgery, hear us out.

The research, published in The Lancet, suggests that the risk of serious heart problems following surgery nearly doubles if it is performed in the morning as opposed to the afternoon, and it’s all to do with your circadian rhythm, otherwise known as your biological clock.


"Our study found that post-surgery heart damage is more common among people who have heart surgery in the morning," lead author David Montaigne, a cardiologist at the University of Lille, told AFP. "The time of day – that is, the biological clock or circadian rhythm – influences the patient's reaction to this kind of operation."

The circadian rhythm is the body’s 24-hour internal clock, governing various cycles and behaviors such as our sleep and waking patterns, body temperature, and even athletic prowess throughout the day-to-night cycle.

The researchers think their findings could be explained by the heart being stronger and better able to withstand the stress of surgery in the afternoon. We already know that heart health fluctuates throughout the day. The risk of heart attacks or strokes is statistically higher in the morning but the heart and lungs work at their peak performance in the afternoon.

To test this out, the researchers looked at the medical history of almost 600 patients who had had surgery to replace heart valves, half having had their surgery in the morning, the other half in the afternoon. They discovered 54 of the 298 morning patients had suffered some kind of major cardiac event in the 500 days following surgery, compared to just 28 of the 298 afternoon surgery receivers.


Following this, the doctors carried out a year-long clinical trial with 88 patients scheduled randomly for morning or afternoon valve replacement surgery. Their findings revealed not only did the tissue from the afternoon group show less damage and repair more quickly, but that multiple genes linked to circadian rhythms were more active in the afternoon group, which shows the heart is also influenced by our body clocks.

One of the most obvious questions, which the researchers have already discounted is, if the body clock affects the heart, then perhaps the surgeons are also affected? But the researchers argue that they strenuously controlled for this and that survival rates were not affected.

So, what is the outcome of this? If you have heart surgery scheduled in the morning should you immediately cancel it? The answer, of course, is no. If you have surgery scheduled at all, then you obviously need it.

The study authors suggest instead that this revelation may help schedule more high-risk or pressing surgeries, for example, those that suffer from obesity or type 2 diabetes have been shown to have an increased risk of complications post-surgery, so their results could, in fact, increase post-surgery success.


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