Having heart surgery in the the morning could double your risk of suffering complications, new research suggests.
The study, published in the Lancet journal, investigated the likelihood of patients suffering complications - such as heart attacks, heart failure or death after surgery - at different times of the day.
The researchers found patients who received surgery in the afternoon had around half the risk of complications compared to patients who had surgery in the morning.
However, they stressed that this was not due to tiredness of surgeons but instead, was likely due to the changes our body undergoes during the day due to our circadian rhythm, or body clock.
The researchers looked at data from 596 open heart valve surgeries in order to asses the impact of operation time.
In the 500 days after surgery, a total of 54 out of 298 morning patients (18%) experienced a “major cardiac event” such as heart attack or heart failure.
In comparison, just 28 out of the 298 afternoon patients (9%) experienced adverse events.
The researchers suggested that our hearts may be better equipped to deal with surgery in the afternoon as they may be stronger this time of day due to the impact of our body clock.
One of the researchers involved in the study, Proffesor Bart Staels, told BBC News patients should not be deterred from having surgery due to the findings.
“We don’t want to frighten people from having surgery - it’s life saving,” he said, adding that it would be impossible for hospitals to only conduct afternoon operations.
“If we can identify patients at highest risk, they will definitely benefit from being pushed into the afternoon and that would be reasonable,” he added.
Commenting on the study Dr Mike Knapton, associate medical director at the British Heart Foundation, said “thousands of people now have open heart surgery in the UK”.
“These procedures can take many hours and come with a number of risks. The time of day appears to be a significant factor in the outcome from surgery, with better outcomes if your surgery is in the afternoon,” he said in a statement.
“If this finding can be replicated in other hospitals this could be helpful to surgeons planning their operating list, for non-urgent heart surgery.
“The study also suggests that modifying the genes responsible for this phenomenon could lead to the development of new drugs to protect the heart from damage during open heart surgery.”
Dr John O’Neill, from the MRC Laboratory of Molecular Biology, added that it’s not surprising that our hearts might be better able to cope with afternoon surgery.
“Scientifically it is not hugely surprising, because just like every other cell in the body, heart cells have circadian rhythms that orchestrate their activity to anticipate the external rhythm of night and day – i.e. our heart ‘expects’ to work harder during the day than at night, with the opposite being true in mice,” he said in a statement.
"In healthy individuals, not engaged in shift work, our cardiovascular system has the greatest output around mid/late-afternoon, and explains why professional athletes usually record their best performances around this time. In the morning, just after we’ve woken up, the cardiovascular system is not yet at peak performance, which partly explains why heart attacks and strokes are occur more frequently in the morning.”
The study is published in the Lancet journal.