COPENHAGEN, DENMARK. Researchers at the Danish Institute of Cancer Epidemiology report that women who predominantly work at night have a 50 per cent higher risk of developing breast cancer than do women who mainly work during the day. Their study involved 7035 women with breast cancer and 7035 healthy controls. The researchers found that women who had worked predominantly (more than 60 per cent) at night for as little as six months of their working career had a 50 per cent greater incidence of breast cancer. The risk increase was particularly pronounced among flight attendants and catering employees and rose to 70 per cent with long-term (longer than six years) nighttime employment. The increased risk was independent of social status, number of children, and other known breast cancer risk factors. The researchers conclude that exposure to light during the night suppresses the production of melatonin. Melatonin has been found to protect against tumor development, possibly through an enhanced immune response and the scavenging of free radicals. Editor's Note: Even exposure to relatively weak light during the night rapidly decreases melatonin production. It may well be that one of the best protective measures against breast cancer is to sleep in a totally dark room.
Hansen, Johnni. Increased breast cancer risk among women who work predominantly at night. Epidemiology, Vol. 12, January 2001, pp. 74-77