Don’t get injured at night… Researchers discover cell repair driven by circadian rhythm; wounds heal 60% faster during the day

Are you scheduled for some kind of surgery in the near future? You might want to request that it take place in the daytime. A recent study by researchers from the U.K.’s Medical Research Council (MRC) Laboratory of Molecular Biology, published in the journal Translational Medicine, has found that wounds inflicted during the day heal up to 60 percent faster than those that happen at night.

The researchers found that not only are the skin cells that repair cuts and burns more efficient in the daytime, but more collagen is also deposited at the wound site immediately after and for the following two weeks after a daytime wound takes place – ensuring a more efficient healing process.

The researchers’ findings were based on laboratory tests using skin cells called fibroblasts and keratinocytes, as well as from studies with mice.

The Daily Mail, reporting on the study, noted:

[D]uring the internal body clock’s ‘daytime’, wounds to the skin healed almost twice as efficiently as wounds incurred during the night. …

The researchers said faster healing took place because skin cells carried out faster repairs at the site of the wound to repair it much faster during the body clock’s daytime.

The difference between daytime and nighttime healing is one of the many facets of the human body controlled by the circadian rhythm – also known as the body clock. The body clock controls everything from sleeping to hormone secretion, and even how quickly you metabolize food.

Dr. John O’Neill, the study’s senior author explained, “This is the first time that the circadian clock within individual skin cells has been shown to determine how effectively they respond to injuries. We consistently see about a two-fold difference in wound healing speed between the body clock’s day and night. It may be that our bodies have evolved to heal fastest during the day when injuries are more likely to occur.”

Amazingly, this process was not governed by signals between cells, but by circadian clocks within the cells themselves, since the results were derived from human and mouse skin cells grown in laboratory dishes.

The cell repair was mainly driven by a protein called actin, filaments of which provide movement and structure, acting like muscles within the cell.

This study has huge implications for the future of surgery.

O’Neill noted, “In both cells and mice, we can reset the tissue healing response by tricking the cells into thinking it’s a different time of day – such as by turning the lights on at night and off at different times of day for the mice, or using body clock-altering drugs on cells in the lab.” He added, “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.”

This improved daytime healing is true of burns, too. As part of their study, the researchers examined the healing patterns of 118 burn patients registered in a major burn unit database in England and Wales. They found that burn victims who were burnt at night – between 8 p.m. and 8 a.m. – took about 60 percent longer to heal than people who sustained their burns during the day – between 8 a.m. and 8 p.m.

In fact, those who received their burns in the day were 95 percent healed within just 17 days, while those who were burnt at night took about 28 days to achieve the same level of healing. (Related: New “smart” bandages will dramatically cut healing time for wounds in chronic patients.)

The researchers are eager to engage in further research to determine whether changing surgery times or using drugs to reset patients’ circadian rhythms prior to surgery might result in better and faster healing. (Related: Discover all the latest medical breakthroughs at

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