Women who are "morning people" are less likely to develop breast cancer than those who are the sharpest in the evening.
Research involving more than 400,000 women found that "larks" have a breast cancer risk that is up to 48 percent lower than "night owls".
The researchers, led by the University of Bristol, also showed that women who slept longer than recommended sleepers for seven to eight hours per night increased their chances of finding a diagnosis by 20 percent for each additional hour they slept. One explanation may be that those who work better in the morning slept better and woke earlier.
The researchers also found that women who slept longer (picture in picture) than the recommended seven to eight hours per night, increased their chances of diagnosis for each additional hour of sleep by 20 percent
And those who are sharper in the evening may have had more sleep disturbances that could affect the risk of cancer.
Researchers believe that later waking up can also affect a woman's body clock, further increasing the risk. This is due to earlier studies of night workers and increased risk of cancer in those exposed to more artificial light at night.
The research team, which presented its findings at the National Cancer Research Institute's Glasgow conference, analyzed women's genes and asked them if it was a person in the morning or evening.
The study, which involved more than 400,000 women, found that "larks" have a breast cancer risk that is up to 48 percent lower than "night owls". Pictured is a picture of a woman performing a breast cancer checkup
Dr. Bristol's Rebecca Richmond said, "We would like to continue working to investigate the mechanisms that underlie these outcomes, as the estimates are based on morning or evening preference issues, not whether people will get up sooner or later the day.
"It can not be that changing your habits changes the risk of breast cancer. It can be more complex than that. "
Dr. Emma Pennery of the charity Breast Cancer Care said, "Changing your sleep habits is not as easy as other proven mitigating measures because they are often part of jobs, parenting or other health conditions."