If you are working on night shifts regularly, chances are your body's ability to repair DNA damage may get hampered, suggest researchers led by one of Indian-origin.The findings suggested that night shifts suppress the production of 'sleep hormone' melatonin.It revealed that a night shift worker produced lower levels of a chemical by-product of active DNA tissue repair called 8-OH-dG in the urine than his day counterpart, leading cells to harbour higher levels of DNA damage.This indicated a reduced capacity to repair cellular damage, the study said.The key factor behind this observed difference was likely to be suppressed production of the 'sleep hormone' melatonin during day sleep relative to night sleep, the researchers said."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," said Parveen Bhatti from the Fred Hutchinson Cancer Research Centre in Washington."This likely reflects a reduced capacity to repair oxidative DNA damage due to insufficient levels of melatonin and may result in cells harbouring higher levels of DNA damage," he continued."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," Bhatti added.For the study, published online in the journal Occupational and Environmental Medicine, the team measured 8-OH-dG levels in the stored urine samples of 50 night shift workers, who exhibited the widest discrepancies in levels of circulating melatonin between night work and night sleep.An 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.