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A recent study published in the scientific journal Current Biology has examined the effects of irregular sleeping patterns on cancer risk and unequivocally concluded that they increase the risk of developing the disease.
Such sleeping patterns include those caused by working in shifts, as so many professions require. Though working in shifts may provide certain advantages to some, such as better childcare options, amounting scientific literature comes to suggest that significant changes to our normal sleeping cycles may lead to dire health consequences.
“Circadian [body clock] disruption can accelerate the development of breast cancer,” Dr. Michael Hastings, UK Medical Research Council said in a statement for the BBC.
Researchers worked with lab mice whose body clocks had been delayed by a total of 12 hours every week over the course of the week. Not only did the animals display a tendency towards weight gain (on average, the animals were 20% heavier than their normal-sleeping counterparts despite receiving the same amounts of food), but they also displayed a higher likelihood of developing tumors.
Normally, laboratory mice would develop tumors after 50 weeks, however, after the team of researchers systematically disrupted their sleeping patterns, they noticed that the mice in the irregular sleeping pattern group developed tumors eight weeks earlier.
“This is the first study that unequivocally shows a link between chronic light-dark inversions and breast cancer development,” the report read.
According to lead author Bert van der Horst, the changes in sleep patterns that the mice experienced mimicked those that a flight attendant would experience if flying to Hong Kong from New York and returning one week after that.
The research team notes that women with a family risk of breast cancer should seek jobs where working in shifts is not required. Their work focused on mice displaying the equivalent of the BRCA gene, responsible for an increased breast cancer likelihood in women.
Notably, there are other confounding factors to be taken into consideration. For instance, the people working in shifts may also be subjected to other cancer-causing factors such as social class, activity levels or vitamin D deficiencies.
Another difficulty lies in interpreting what the consequences would be for humans suffering the same sleep pattern differences that the mice were subjected to. Researchers explain that the estimated weight equivalent would be approximately 10kg. In the case of at-risk women, they estimate that they would get cancer approximately five years earlier than if she would if she would not work shifts.
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