Irregular sleeping patterns have been "unequivocally" shown to lead to cancer in tests on mice, a study suggests. The report, in Current Biology, lends weight to concerns about the damaging impact of shift work on health. The researchers said women with a family risk of breast cancer should never work shifts, but cautioned that further tests in people were needed.
The data also indicated the animals were 20% heavier despite eating the same amount of food. Studies in people have often suggested a higher risk of diseases such as breast cancer in shift workers and flight attendants. One argument is disrupting the body’s internal rhythm – or body clock – increases the risk of disease. However, the link is uncertain because the type of person who works shifts may also be more likely to develop cancer due to factors such as social class, activity levels or the amount of vitamin D they get.