Night shifts double breast cancer risk

Studies have shown that women who work as nurses on night shifts have an increased risk of developing breast cancer.  And now new research suggests that that’s also true for female night shift workers other than nurses. A study published in Occupational and Environmental Medicine has found that women who work night shifts for 30 or more years double their risk of developing breast cancer.  Risk factors can include hormone sensitivity – including the sleep hormone melatonin – and the disruption of normal estrogen production cycles.

Canadian women from two major cities were interviewed about their careers and breast cancer history, accounting for a total of 1,134 who had been diagnosed with the condition and 1,179 women who had not.  The women had worked in a variety of jobs, but the incidence of breast cancer doubled among the women who said they had worked night shifts for significant periods of their lives.  Those who had worked nights for up to 29 years showed no increased risk, while those who did so for more than 30 years were twice as likely to develop the disease.

The study authors believe that sleep disturbances--which upset body rhythms, including hormone production—lack of vitamin D and lifestyle differences may play a role in the increased risk.

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Sourced from:, Long Term Night Shifts Linked to Doubling of Breast Cancer Risk