When we are tired or injured, we often go to bed earlier to recharge and mend our bodies. That's because we often think that night is a golden time to deal with stress or injuries. But is it true?

Nathaniel Hoyle, a scientist of the Laboratory of Molecular Biology in Cambridge, UK, has been leading a study into this topic. The team discovered that fibroblast cells(成纤维细胞) in the body switch off at night. These cells help close up a wound after the skin is broken and lay a foundation for new skin to grow. Why exactly are these cells less active at night?

It's all to do with your body's circadian (昼夜节律的) rhythm—a 24-hour internal clock that helps your cells do their jobs on time. New Scientist reported that a group of 30 genes that control the fibroblasts worked only daytime shifts, causing the slower healing process at night.

To test its theory, the Cambridge-based team examined data from the International Burn Injury Database, which records details of burn victims around the world. This analysis revealed that nighttime burns, on average, took 11 more days to heal than burns during the day.

A similar result occurred while experimenting using live mice. Those that were cut during night-time hours recovered more slowly than those during the day. "You can see by eyes, when the cell is wounded only 8 hours apart from each other, in a different circadian periods, the daytime wounded ones take off, and the nighttime ones drag," research team member John O'Neill told Science Alert.

He added, "The time-varying response may be an evolutionary adaptation. As people are more likely to sustain injuries when awake than when sleeping, perhaps our bodies are prepared to respond more quickly in the daytime." He went on to say that it could be beneficial to schedule surgeries in time with people's circadian rhythms, earlier for early birds and later for night owls, in order to lessen recovery time. However, in any case, it might be best not to use anything sharp once the sun goes down.