Night shifts may hamper DNA repair: study

Working in night shifts may hinder the body's ability to repair DNA damage caused by normal cellular processes, scientists including one of Indian origin warn.
Researches including those from Duke University in the US had previously had found that day sleep was associated with lower levels in their urine of a chemical by-product of active DNA tissue repair called 8-OH-dG than night sleep-potentially indicating reduced capacity to repair cellular damage.
In the new study, they measured 8-OH-dG levels in the stored urine samples of 50 night out of the 223 night shift workers.
These 50 people had exhibited the widest discrepancies in levels of circulating melatonin between night work and night sleep.

Analysis of the urine samples showed that melatonin levels were much lower when taken during a night shift than when taken during a normal night's sleep, researchers said.
After taking account of potentially influential factors, such as alcohol consumption and shorter sleep duration (average 5.5 hours) during the day preceding a night shift, 8 -OH-dG levels were only 20 per cent of those observed during a normal night's sleep (average 7.5 hours).

"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," researchers including Parveen Bhatti from Fred Hutchinson Cancer Research Centre in the US said.

A particular pathway called NER is thought to be involved in the repair of DNA damage caused by oxygen free radicals, which are produced during normal cellular activity, researchers said.
Research has shown that melatonin production boosts the activity of the genes involved in the NER pathway, they said.
The study was published in the British Medical Journal.