WORKING night shifts could hinder the body’s ability to repair DNA damage, a study has found. Research suggests suppression of sleep hormone melatonin, which regulates the body clock, may be behind the findings, which could be linked to a cancer risk.

The claims are published in the Occupational & Environmental Medicine online journal and follow research on more than 220 people.

Initial tests found sleeping during the day was associated with lower production of 8-OH-dG, a chemical by-product of active DNA tissue repair. Lower levels of the substance, as found in the urine of test subjects, are said to indicate a reduced capacity to repair cell damage.

Follow-up work on a 50-strong group by a specialist cancer unit in Seattle measured 8-OH-dG at just 20 per cent of that observed during a normal night’s sleep of around 7.5 hours. The findings are said to relate to the repair of DNA damage caused by oxygen free radicals, which are produced during normal cellular activity and have been implicated in the development of cancer.

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.

“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.

“If such effects are confirmed, melatonin supplementation should be explored to reduce the occurrence of potentially carcinogenic DNA damage among shift workers.”