The alleged connection between a disrupted body clock and an increased risk of cancer has been disproven by new research published in the United Kingdom.
It's good news for women who regularly work night shifts who may have been concerned about their possible risk of developing breast cancer.
The research, published in the Journal of the National Cancer Institute, has debunked previous studies that suggested the disruption to the human body clock caused by night-shift work was a possible cause of cancer.
Funded by the Health and Safety Executive, Cancer Research UK and the UK Medical Research Council, the latest study followed 1.4 million women who took part in 10 different studies as it examined whether or not night shift work increased a woman's risk of breast cancer.
Jean Hailes endocrinologist Dr Sonia Davison says the artificial light that the body was exposed to during night shift had been thought to disrupt the natural daily pattern of hormone production. Previous studies suggested this may have been linked to the development of breast cancer.
In this latest study, researchers compared those who had never done shift work to those who had, including those who had worked up to 20 or 30 years in night shift to see if there was any increased risk of breast cancer.
The study found no increased risk of breast cancer in the shift-working participants.
Dr Davison believes the study is "reassuring for women all over Australia who do vital work during night shifts," particularly those who had worked night-shift long-term.
"Of the 1.4 million Australians who work night shifts, up to 15% of these are women, with most being employed in healthcare, social assistance, food and accommodation industries," she says. "The largest number of shift workers are in the healthcare and social assistance sectors, which has 25% or 342,900 workers, of which 45% are women."
Dr Davison says it's also important for women working night shifts to ensure they get enough exercise, eat a balanced diet and make time to socialise with friends and family each week to avoid burnout.
See our recent story on foods and snacks that can fuel you through the night shift.