Time of day may affect surgical outcome
DEAR DOCTOR: It seems like doctors always want to schedule surgeries as early as possible. But I recently read that heart surgery survival chances are better in the afternoon. Why would this be?
DEAR READER: You’re referring to the results of a study published in the journal Lancet last month. Over the course of six years, scientists from the University of Lille in France examined the medical data of close to 600 patients who underwent a heart surgery known as aortic valve replacement. The researchers wanted to know whether the time of day that these surgeries took place played a role in which patients went on to experience serious complications.
The results were surprising. Researchers found that patients whose surgeries were performed after noon had half the risk of heart attack, acute heart failure or death in the 500 days after surgery than did those whose procedures took place in the morning.
The findings seem to add to a growing body of evidence that circadian rhythms — that is, our biological clocks
— have an effect on health-care interventions. Previous studies in mice have suggested that the body responds best to chemotherapy during certain times of day. A large-scale study into flu shots found that, among older people, those who received the vaccine in the morning produced more antibodies than those who got an afternoon injection.
Previous research has shown that circadian disruption affects learning, mental and emotional health, and can even lead to death. This line of inquiry is considered to be so important that last year the Nobel Prize in Medicine went to three researchers who identified the molecular mechanisms that control our body clocks.
There are certain caveats regarding the new heart surgery study. As an analysis by the National Institutes of Health notes, 600 patients make a small sample size. Each of these patients was treated at the same hospital, which raises the question whether it was the time of day of the surgeries, or the specific surgical teams that performed them, that had the greatest effect on the outcomes.