Night work detonates breast cancer

• May 5, 2024

The night work or working in that shift for more than 30 years doubles the risk of breast cancer, suggests a new study of the Queen's Cancer Research Institute at Queen's University in Kingston, Ontario, Canada, published online on July 1 in theJournal Occupational and Environmental Medicine.

The study found an apparent relationship between night work and the risk of breast cancer, but did not demonstrate the existence of a cause-and-effect relationship.

Other investigations have found a relationship between night work and breast cancer, especially for health professionals. But the new study revealed an apparent risk, among other types of workers, according toKristan Aronson, lead author of the study and professor of Public Health Sciences at the Institute .

While women with 30 or more years of night work had double the risk, the Aronson team did not find an increased risk among those who worked at night for less than 30 years.

The researchers obtained very specific data about the history of women's work. "We were very careful when asking about life-long work histories, including the specific start and end times of each shift, so we carefully evaluated the exposure of each woman to the night work "explained Aronson.

Aronson's team observed more than 1100 women with breast cancer and others more than 1100 without the diagnosis who were of the same age and lived in Vancouver or Kingston. On average, the women were between the middle and late 50s. Some had already gone through menopause, while others have not yet.

The women who participated answered questions about their patterns of work . In as much, the investigators obtained information on the diagnoses of cancer of the hospital registries. In this regard, they observed that about a third of the women in each group once worked on the night shift.

When Aronson analyzed the groups of women regarding the duration of the night work , found that there was a link between working 30 years or more and double the risk of breast cancer, which was maintained even after taking into account other factors that may affect cancer risk, such as body mass index.

"So far there is only hypothesis about what could be linked in the long term shift work, to an increased risk of breast cancer," he explained.

"Some of these hypotheses are: alteration of the normal daily rhythm of the body (circadian), decrease in melatonin (hormone that regulates the sleep-wake cycles that occurs in greater quantity during sleep), the increase in sleep disturbances and the possible low of vitamin D. "

The findings echo previous research, says Russel Reiter, researcher at the University of Texas Health Science Center in San Antonio , who has also studied the subject. "The strength of the study is the number of people included," he said. "In general terms, the association between the night work and breast cancer. "

Among the possible explanations, it coincides, is the suppression of melatonin. The night work It can affect the levels of melatonin, which, some experts believe, can help strengthen the immune system.

In addition to preventive care, such as mammograms, what can women who have night work ? While many of them do not have the option to change jobs, they could choose this type of shift for less than 30 years, says Aronson.

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