Shift work is necessary in many important professions, including protective services like police and firefighters, health care, and transportation. Some shift workers say that working outside of the traditional 9 to 5 hours provides them with certain advantages, like a more convenient childcare situation, but a growing body of evidence shows that straying too far from the natural cycle of sleeping at night and waking during the day has serious health consequences.
The latest addition to this growing body of evidence is a study published in the journal Current Biology that reports that mice subjected to a schedule similar to those many shift workers experience not only gained about 20 percent more weight, but also developed breast cancer much earlier in life than those on a more natural schedule.
"In real life this mimics the situation encountered by a flight attendant that would fly from New York to Hong Kong - a 12-hour time difference - and return the week thereafter," senior study author Bert van der Horst of Erasmus University Medical Center told Tech Times.
It is important to note that the mice used in the study had the mouse equivalent of a BRCA gene. In both humans and mice, particular genes can significantly increase the risk of developing breast cancer - Angelina Jolie fans will remember that the actress recently got a double mastectomy because she carries the gene BRCA1. Still, compared with other breast cancer-prone mice, which typically develop breast cancer at an age of 50 weeks, those on a shift work schedule developed breast cancer about 8 weeks earlier in life.
The 24-hour biological cycles that go on within the bodies of not just humans, but many organisms including mice, are known as circadian rhythms. Studies such as this one suggest that 'circadian disruptions' like those experienced by shift workers are often harmful to health, but studying this phenomenon in humans is very challenging due to the many different factors at play in people's lives.
Mimicking the circadian disruptions that humans experience in a controlled setting using mice is a way for researchers to identify particular factors that they should pay attention to when studying humans, which are in many ways similar, but much more complex to study.
"We have shown that this mouse model so well translates to the human situation," van der Horst said. "We can now start to explore in detail which factors in shift work are causing the increased cancer vulnerability and how to counteract them with well-designed intervention strategies, which subsequently can be validated in well-designed human studies."
Photo: Giang Hồ Thị Hoàng | Flickr
