A new study hints at increased risk of breast cancer in women who work night shifts.
Empirical evidence shows that night work disturbs the circadian rhythm of the human body - an internal clock that controls numerous biological functions.
But to find out if work that disturbed the circadian rhythm was carcinogenic, researchers from the French human health research body, Inserm, examined the careers of 3,000 French women between 2005 and 2008.
They found that the risk of developing breast cancer was 30 percent higher in those women who had worked nights compared to those who hadn't. Among the women, eleven percent had worked night shifts at some point in their career.
Increased risk was particularly noticed in women who had worked nights for over four years, or in women whose working rhythm was less than 3 nights per week, because this led to more frequent disturbances between night and day rhythms.
The link between night work and breast cancer seemed to be more marked in women who had worked night prior to their first pregnancy. The researchers say a possible explanation for this could be that mammary cells, incompletely differentiated in women before their first pregnancy, could be more vulnerable.
According to the American Cancer Society's recent estimates, about 226,870 women in the US would develop breast cancer in 2012 and about 39,510 will die from the disease - the number one cause of female mortality.
The risk factors that trigger this disease include genetic mutations, late first pregnancy, and low parity or hormone therapy. Other causes of breast cancer such as way of life, environmental or professional causes have not yet been completely identified.
by RTT Staff Writer
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