Night Shift Might Lead to DNA Damage

Working the night shift just got a little harder: Researchers say when the body is forced to sleep during the day its ability to repair DNA is compromised, which could lead to adverse health conditions — possibly even cancer.

In a study published June 26 in the Occupational & Environmental Medicine journal, researchers found that people who sleep odd hours produce much less melatonin (which regulates the body's sleep patterns). This lack of melatonin is related to more cellular debris accumulation, which in turn can damage cells and DNA. It's this cell damage that can lead to mutation, or cancer.

Add to that, the conclusion of the study also states that the average person gets less sleep when working the night shift — 5 ½ hours compared to 7 ½. And a lack of sleep has been associated with impaired brain function and cognitive abilities.

The research, led by Dr. Parveen Bhatti, at the Fred Hutchinson Cancer Research Center, in Seattle, Wash., showed that in night workers, critical cell processes are being disrupted, leaving cell damage and destruction to DNA.

Dr. Bhatti and his researchers re-examined 50 night-shift workers from a previous study of 225. The previous study showed that day sleep was associated with lower levels of cellular waste from tissue repair than night sleep — potentially indicating reduced capacity to repair cellular damage. Bhatti showed in his research that this was possibly due to a lack of melatonin in those who sleep during the day compared to regular night sleepers — those who work at night had only 20 percent of the levels of melatonin when compared to those who had conventional sleep hours. Melatonin is crucial for normal gene activity that in turn repairs DNA.

“Our results indicate that, relative to night sleep, reduced melatonin production among shift workers during night work is associated with significantly reduced urinary excretion of 8-OH-dG [cell waste, excreted in urine],” Bhatti said. “This likely reflects a reduced capacity to repair oxidative DNA damage due to insufficient levels of melatonin and may result in cells harboring higher levels of DNA damage.”

Bhatti and his team said further studies might determine whether the supplement melatonin might mitigate the damage to DNA: “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.”