Dutch researchers are suggesting that sleep pattern disruption is a cause of breast cancer development, weight gain and other metabolic problems.

In the study, published in the July 20 issue of Current Biology, researchers from the National Institute for Public Health and the Environment in the Netherlands and at the Erasmus University Medical Center studied mice with a genetic predisposition to breast cancer. They found that the cancer onset – normally at 50 weeks – was eight weeks earlier in mice that experienced circadian rhythm disturbances.

“This outcome is in line with what has been found in epidemiological studies in humans, and now provides strong causal evidence for circadian disruption as a carcinogenic factor,” said senior study author Bert van der Horst of Erasmus University Medical Center.

The mice subjected to alternative light-dark cycles also gained about 20 per cent more weight than those that were not.

“There are not many long-term studies like this in animals, and hardly anybody sees effects on weight gain,” said co-author Harry van Steeg of RIVM. “So to have two endpoints coinciding – early tumour development and weight gain – is surprising.”