Researchers from the School of Medicine, Yale University have discovered that the success of the body’s immune system when it comes to fighting a disease depends on its 24-hour circadian cycle, ie the biological clock . And therefore, at certain times of day we are more vulnerable to attack by viruses and bacteria.


“People know intuitively that when alter their sleep patterns, for example because they wake up at midnight or stay up late because they are more likely to get sick,” says Erol Fikring, epidemiologist and coauthor of the study published in the journal Immunity.

In their experiments revealed that, in mice, the circadian clock controls the activity of a gene of the immune system responds to the presence of viruses and bacteria. The more you express this gene (TLR-9), faces the best body to infection. And if a vaccine is administered at the time of maximum activity of TLR9, immunization is also much more effective.

According Fikrig, the results suggest that interrupt our regular schedule, and therefore alter the circadian rhythm, for example by passing a sleepless night, makes us more vulnerable to invasion by viruses and bacteria. And the jet lag, which occurs when we travel across several time zones, also predisposes us to get flu, colds and other infections.

On the other hand, analyzing what the “peak” of activity of the gene throughout the day (and night) in different individuals could result in therapeutic strategies designed to optimize the immune response and protect patients at the time are most vulnerable. For now, we know that between 02:00 and 06:00 in the morning are more severe infections and mortality risk is higher, especially in intensive care units (ICUs) in hospitals. Avoiding artificial light to respect the sleep of patients in these units, and removing noise at certain times, preventable complications, concludes Fikring.