Night Shift Work May Raise Cancer Risk, Say Researchers

That evidence included a higher rate of breast cancer in female nurses who work in night shifts, said the report published on online edition of health magazine WebMD.

The scientists also reviewed studies in which animals were exposed to light at night, disrupting the animals' circadian rhythm - the regular changes in mental and physical characteristics that occur in the course of a day.

They found sufficient evidence of a connection between circadian rhythm disruption and cancer, the report published in the journal 'The Lancet' said.

'Shift work that involves circadian rhythm disruption is probably carcinogenic to humans,' writes Kurt Straif, who works for the International Agency for Research on Cancer in France.

The scientists noted that night shift work might raise the risk of cancer by suppressing production of melatonin, a hormone chemical involved in the circadian rhythm.

They also mentioned in their report that people working as a painter are carcinogenic, and those who work as a firefighter are 'possibly carcinogenic' because of the on-the-job chemical exposure.