The time of day of your surgery could have long-term impacts on your health. That’s according to researchers who looked at the way circadian rhythm – the body’s internal clock – affects the outcomes of a patient recovering from a complex heart procedure.
Patients who underwent open-heart surgery in the afternoon experienced better health outcomes compared to those who were operated on in the morning, study authors found after six years of observing nearly 600 patients who underwent heart valve replacement.
In the subsequent 500 days after surgery, researchers found, those patients who were operated on in the afternoon had half the risk of a major cardiac event – for instance myocardial infarction, acute heart failure, or death – as those who underwent surgery before then.
The team also conducted a randomised controlled trial of 88 different patients who underwent the same surgery, half in the morning and the other half in the afternoon. They found that afternoon surgeries resulted in lower levels of myocardial ischaemia-reperfusion injury – tissue damage that occurs when blood flows again through the repaired portion of the heart – than did morning surgeries.
Experts say that sort of heart tissue injury can lead to higher risk of short- and long-term mortality.
University of Lille-France professor David Montaigne, the study’s lead author, suggested that the study’s findings indicate that scheduling changes could decrease injury or death.
“There are few other surgical options to reduce the risk of post-surgery heart damage, meaning new techniques to protect patients are needed,” Montaigne said in a statement. “Our findings suggest this is because part of the biological mechanism behind the damage is affected by a person’s circadian clock and the underlying genes that control it.”
The findings are the latest in a growing body of evidence suggesting that time of day plays an important role in how well various medical treatments work. Studies show that the efficacy of some vaccines and cancer treatments may be affected by the time of day when a therapy is administered or medicine is taken. For example, research has found that patients who received a seasonal flu vaccination before 11.00am produced more antibodies than those who received a vaccination after 3.00pm.