Working night shifts does not increase the likelihood of developing breast cancer despite previous evidence to the contrary, a study has found.
The research, published in the British Journal of Cancer, found women who work overnight are no more likely to develop the disease than those who work regular hours.
The findings will provide reassurance to thousands of workers, following decades of debate over the link between night shifts and breast cancer.
It was first suggested in the 1970s that exposure to electric light may increase the risk of developing the disease, by potentially disrupting the body’s internal clock, suppressing levels of the sleep hormone melatonin and raising oestrogen levels.
In 2007, the International Agency for Research on Cancer, part of the World Health Organisation, said that shift work which disrupts the sleep cycle is “probably carcinogenic”.
The new study, funded by charity Breast Cancer Now, included data from 102,869 UK women over 10 years, 2,059 of whom went on to develop invasive breast cancer.
Analysis by the researchers found no overall link between night shift work and the likelihood of developing breast cancer.