Breast Cancer: Women Working in Night Shifts are at Greater Risk

Breast Cancer: Women Working in Night Shifts are at Greater Risk

May 29, 2012: The Danish researchers have found that the women who work for at least three night shifts for about six years or more were more likely to develop breast cancer than those who did not work at nights. These women were two times likely to become victim of breast cancer compared to other women.

Amongst these women, the women who described themselves as morning people (larks) were four times likely to develop breast cancer than those who did not work at nights. Even though less affected by night shifts, the women who consider themselves as ‘owl’s were still twice more likely to develop cancer than those not at all working at nights.

The disruption to the body clock and the changes in the levels of melatonin (‘darkness’ hormone) along with the lack of sleep are thought to be responsible for the development of breast cancer in women.

Breast cancer test

The study included the examining of 18,500 women’s medical records, who worked for the Danish Army anywhere between 1964 and 1999. The researchers also contacted 210 women out of the total 218 women who were victimised by the breast cancer between 1990 and 2003. Later, these women were compared with the other 899 women of the same age who had not developed the disease despite having worked for the Danish Army.

Finally, the 141 women with breast cancer and 551 women free from disease answered a detailed questionnaire of 28 pages dealing with their lifestyle, sunbathing, family and whether they took hormone replacement therapy as well as contraceptives or not.

Dr. Johnni Hansen of the Institute of Cancer Epidemiology in Copenhagen, Denmark, stated in the journal Occupational and Environmental health, “We observed a neutral risk for breast cancer associated with any duration of night shift work among women with only one or two shifts per week.” The lead author, Dr. Hansen further wrote, “This is consistent with the observation that one or two night shifts will not change the timing of melatonin production and thereby not initiate circadian disruption.”

In addition to this, Dr. Hansen has also warned that the findings of the study might be an underestimate of the effect of working at night on breast cancer as the study involved only women who were breast cancer patients and still alive. He added, “The observation that women with night work and morning preference (who may be less tolerant of night shift work) tend to have a higher risk for breast cancer than similar women with evening preference warrants further exploration in larger studies.”

“Research onto shift-work is focussing on disruption of the body clock’s regulation of melatonin, the hormone of the night’, which may also have some ‘anti-breast cancer properties’,” said Prof. Jim Horne of the Sleep Research Centre at Loughborough University. “‘Larks’ are well known to have more difficulty in coping with shiftwork, and may be more stressed by it, which will also interfere with melatonin.”

The Senior Police Officer at Breakthrough Breast Cancer, Dr. Rachel Greig commenting on the study said, “We know that shift work is associated with an increased risk of breast cancer, and this study further supports this view.” He further added saying, “The exact reasons are still not known and it may be that night shifts themselves are not the only cause, as shift work can increase the likelihood of other lifestyle risk factors, such as lack of exercise.”

Dr. Greig has also suggested the women to cut back on alcohol and regularly exercise as well as maintain healthy diet in order to bring down the risk of breast cancer.

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