According to the researchers, the risk of serious problems after open heart surgery almost doubled if the surgery is not performed in the afternoon and in the morning.
Experiments and laboratory tests have shown that the biological clock is the main reason for the striking difference in the results, reported in the medical journal The Lancet.
"The study showed that heart problems are more common after surgery if it was held in the morning, - says lead author David Montaigne, a cardiologist at the University of Lille. - The biological clock (circadian rhythm) affect the response of the patient. "
Circadian clocks regulate daily body cycles, affecting sleep, hormone release and even body temperature. In case of violation of rhythm it can worsen depression, bipolar disorder, cognitive function and impair memory formation. Earlier this month, the Nobel Prize in Medicine was awarded to three American scientists who first introduced as a "ticking" circadian clock.
The new study was conducted in four phases. First, the researchers looked at the medical records of nearly 600 people who had undergone surgery to replace heart valves. Then, for a long clinical trial, 88 patients were selected for surgery in the morning and afternoon hours. At day patients had fewer problems with the tissues.
Genetic analysis of these tissues showed that hundreds of genes associated with circadian rhythms were more active in the daytime group, indicating that the heart is also affected by the biological clock.
Montaigne and his team removed and replaced with the corresponding genes in mice to study the transition between sleep and wakefulness, and vice versa. They have identified drugs that could affect these genes in such a way as to protect the heart during surgery.
"The study clearly showed that the circadian rhythm is of clinical importance", - commented Michel Oviz, a cardiologist from the hospital Louis Pradel, France. According to him, high-risk patients is better to carry out operations in the afternoon.
John O'Neill from the Laboratory of Molecular Biology of the Medical Research Council in Cambridge believes that the results are accurate, but predictable.
"Like other cells in the body, heart cells have circadian rhythms that organize their activities, to determine the rhythm of day and night, - he says. - Our heart expects that there will be more work during the day than at night. But the discrepancy in the results between the morning and afternoon operations may also be explained by differences in the biological clock surgeons. We know that hand-eye coordination, concentration and cognitive abilities depend on the time of day. Circadian rhythms can affect the results of operations on the heart, but an understanding of how to use this information requires further investigation. "
It was shown that the "owls" and "larks" different genetic chronotype to determine whether the body to function better in the afternoon or at night.