Link Between Long Term Night Shift Jobs and Breast Cancer

Women working night shifts have an increased risk of developing breast cancer, studies suggest.

Studies carried out by researchers from Queen’s University and University of British Columbia, Canada, and Drexel University in the US have found that women who worked night shifts for 30 years or more were twice as likely to develop breast cancer. In addition, two independent epidemiologic studies have provided evidence about another potential risk factor - the amount of light at night.

Researchers reviewed women working in many different roles. One hypothesis involves the hormone melatonin which it has been suggested has cancer protective properties. Exposure to light is known to reduce production of melatonin. So night shift workers going from a day environment to an artificial light environment at night will have lower levels of this hormone.

No link has been found between higher breast cancer risk and periods of night work which were shorter than 30 years.

Further information can be found in the Oxford Journal