Wounds sustained between 8pm and 8am take far longer to heal, scientists discover

It is a sobering thought when stumbling home from the pub. According to scientists injuries sustained at night take far longer to heal.

Likewise, recovery will be faster if you burn yourself cooking Sunday lunch compared with making a late supper supper.

The bodily quirk was discovered after scientists at the Medical Research Council in Cambridge monitored the recovery times of 118 burns victims.

They discovered that those burned between 8pm and 8am took on average 28 days to recover compared with just 17 days for those injured in the daytime.

Scientists believe that the human body clock is not evolved to handle wounds at night, because our ancestors would not have been active in the dark.

Dr John O'Neill, senior author on the paper from the MRC Laboratory of Molecular Biology, said: "This is the first time that the circadian clock within individual skin cells has been shown to determine how effectively they respond to injuries.

“It may be that our bodies have evolved to heal fastest during the day when injuries are more likely to occur.

"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."

Our body clocks - or circadian rhythm - regulate nearly every cell in the human body, driving 24-hour cycles in many processes such as sleeping, hormone secretion and metabolism.

Initial tests using skin cells - fibroblasts and keratinocytes - and also in mice showed that during the internal body clock's 'daytime', wounds to the skin healed almost twice as efficiently as wounds incurred during the night.

The researchers found that this effect was mirrored in humans with burns, whose skin cells were found to move to the site of the wound to repair it much faster if the injury happened in the daytime.

In daytime wounds, there was also more collagen - the main structural protein in skin - deposited at the wound site, which continued for up to two weeks after the wound occurred.

Dr Ned Hoyle, lead author on the paper from the MRC Laboratory of Molecular Biology, said: “Efficient repair of our skin is critical to preventing infection, and when healing goes wrong wounds can become chronic or excessive scarring can occur.

“Further research into the link between body clocks and wound healing may help us to develop drugs that prevent defective wound healing or even help us to improve surgery outcomes."

Dr John Blaikley, an author on the study and clinician scientist from the University of Manchester, who contributed to the analysis of burns patients, said: "Treatment of wounds costs the NHS around £5 billion a year, which is partly due to a lack of effective therapies targeting wound closure.

“This research, for the first time, shows how circadian factors are important for wound healing. By taking these into account, not only could novel drug targets be identified, but also the effectiveness of established therapies might be increased through changing what time of day they are given."

The research was published in the journal Science Translational Medicine.