Wounds That Occur During The Day Heal 60 Percent Faster Than Those That Happen At Night

What time of day you get hurt has a dramatic influence on how quickly that wound will heal. Researchers in the UK have discovered that wounds that occur in the daytime heal up to 11 days quicker than those that have occurred at night, and could pave the way for the development of drugs that would help speed up the recovery of patients.

It turns out that the body clock ticking away inside each and every one of us, known as the circadian rhythm, has a profound impact on how the skin cells that are first to respond damage react. Publishing their results in Science Translational Medicine, the researchers showed how these cells, called fibroblasts, were changing their activity over a 24 hour period.

“This is the first time that the circadian clock within individual skin cells has been shown to determine how effectively they respond to injuries,” said Dr John O’Neill of the MRC Laboratory of Molecular Biology, and senior author of the paper. “For people who had burns, we found quite a big difference in wound healing speed, which agreed perfectly with the predictions.”

The team first tested their theory on mice, showing that wounds that occur during the "active" phase of the circadian rhythm (which for mice is confusingly during the night) were far quicker in healing. They then turned to the records of burns patients who had passed through the NHS, and looked to see if there was any connection between when they were injured, and how long it took them to get better.

Astonishingly, those who were burned at night took an average of 60 percent longer to heal than those who were injured during the day. Nighttime injuries took around 28 days to heal, compared to just 17 for daytime mishaps.  

Looking into the reasons behind this stark difference, the researchers found that the skin cells move into the site of injury much faster during the day than at night, a behavior that was driven by an increase in activity of a protein called actin, known for its role in cell movement and repair.

The discovery could have some pretty incredible applications in medicine by dramatically cutting recovery times.

“It may be that healing time could be improved by resetting the cells' clocks prior to surgery, perhaps by applying drugs that can reset the biological clock to the time of best healing in the operation site,” Dr O’Neill explained.

Interestingly this follows another recent paper that found open heart surgery is more successful if it is carried out in the afternoon than in the morning. It seems then that perhaps we should be tailoring our medicines to the time of day.