Working night shifts for more than 30 years doubles the risk of breast cancer in women, according to new research, which warns the increase may be due to sleep disturbance and a fall in the body’s production of melatonin.
A group of Canadian researchers, who published their findings today, studied 2,500 women with and without the disease – a third of whom had a history of working night shifts.
“An association between 30 years of night shift work in diverse occupations and breast cancer is supported here,” said the researchers.
"As shift work is necessary for many occupations, understanding of which specific shift patterns increases breast cancer risk, and how night shift work influences the pathway to breast cancer, is needed for the development of healthy workplace policy," they said.
Melatonin
The body’s production of melatonin – a pineal hormone which is inhibited by light and which is believed to have several cancer-protecting properties – is known to be lower amongst those who regularly work at night.
Responding to the study’s findings , Dr Jane Green, an Oxford University clinical epidemiologist, said: “[It] does not change the existing consensus: that while there is some evidence to associate increased risk of breast cancer with very long-term shift work, the evidence is not yet sufficient to be sure and certainly not sufficient to give a public health message about working shifts.”
