Here's a study that I, as a night shift-working woman, sincerely hope to be incorrect. The Daily Mail reports that a recent study, backed by the Danish Cancer Society and involving over 18,500 women working for the Danish army between 1964 and 1999, links night-shift work with a 40-percent increased risk of breast cancer, as compared with no night shift work at all.
Women working more than two night shifts a week have double the risk of those on day shifts, says a report from scientists, while night workers who also describe themselves as "morning people" or "larks" have a stronger risk than those who say they are "night owls".
Working frequent night shifts for multiple years is though to disrupt circadian rhythms and sleep patterns. Moreover, the researchers believe that constant exposure to light sources -- computer screens, lamp light, TV screens, etc -- may disrupt in the body the production of melatonin, a hormone that dictates the natural cycles that govern sleep patters and is believe to surpress tumors.
The women completed a detailed questionnaire which included questions on their working patterns, use of the Pill and HRT, sunbathing habits and whether they classified themselves as a ‘morning' or ‘evening' person.
Overall, night shift work was linked with a 40 per cent increased risk of breast cancer compared with no night shifts. But women who had worked night shifts at least three times a week for at least six years were more than twice as likely to have contracted the disease as those who had not.
Still, Dr. Rachel Grieg, of the charity Breakthrough Breast Cancer, maintains that the nigh-shift link is correlative, not causative, as "shift work can increase the likelihood of other lifestyle risk factors, such as lack of exercise."
One question I'd very much like answered is whether taking melatonin supplements at night, to wind down after working a night shift, compensates for the late-night screen light that disrupts natural melatonin production in the body. Because I work at night and take melatonin. And i'm now a little concerned.