Recently scientists have identified one more factor that may increase the risk of breast cancer, prolonged exposure to artificial light. Scientists have found that women, who work in nightshift, have increased risk of breast cancer compared to women who work during regular working hours.

Scientists are speculating that prolonged exposure to artificial light may be the cause of increased breast cancer incidence in the group of women who work in nightshifts. They also acknowledge that other factors like socio-economic status and stress of and strain of working in the night shift may also be contributing to the increased risk. However scientists think that the disruption circadian rhythm resulting from the odd working hours is to be blamed for increased risk of breast cancer.

Disturbances in the circadian rhythm, which is the biological clock within us, causes chronically low levels of melatonin, which is a hormone that is made in our body during dark hours of the day. It has been shown in the past that melatonin has the properties of tumor suppression. Naturally researchers assume that the increased incidence of breast cancer in women who work in nightshifts could be correlation to chronic low levels of melatonin caused by lack of exposure to darkness.

Scientists from Brigham and Women's Hospital in Boston and Harvard Medical School have recently found that women who work in the nightshift may have elevated levels of estrogen hormone compared to women who work during regular hours of the day.

In a study done by the same group of researches have found that those women who regularly works in the nightshift have 1.5 fold increased risk of developing breast cancer compared to women who work in the regular hours of the day. This study results are based on observation of 78,000 nurses for a period about 10 years.

---