Night shift work may stop the body repairing daily damage to DNA and raise the risk of mutations which lead to cancer, a new study suggests.

一项新研究显示，上夜班会阻止身体修复日常的DNA损伤，令基因突变风险增大进而引发癌症。

The link between working at night and poor health has been known for several years, with those who work after dark more likely to suffer diabetes, obesity, poor fertility, heart attacks and tumors.

Scientists believed that disruption to the body’s natural body clock was responsible for the increased risk of chronic illness, but could never pinpoint the mechanism.

Now US researchers have discovered that when people work nights they produce 80 percent less of a chemical which is a by-product of DNA tissue repair. They say it indicates that the body is not carrying out the crucial restoration to cells which should happen naturally overnight.

They believe the effect could be caused by a lack of melatonin, the sleep hormone, which is far lower among people who sleep in the daytime.

They believe that shift workers may need to take sleep hormone supplements to allow DNA to carry out repairs as they sleep in the day.

"If such effects are confirmed, melatonin supplementation should be explored as an intervention to reduce the occurrence of potentially carcinogenic DNA damage among shift workers," added Dr Bhatti.

The research was published in the journal Occupational & Environmental Medicine.