More good news for those smug early risers who can get up at the crack of dawn to do yoga before work: You're less likely to develop breast cancer than night owls.
Analysis showed women who slept longer than seven to eight hours a night - the amount recommended - increased their chances of being diagnosed with the disease by 20% per additional hour spent sleeping.
"We also found some evidence for a causal effect of increased sleep duration and sleep fragmentation on breast cancer, assessed using objective measurements of sleep obtained from movement monitors worn by around 85,000 UK Biobank participants".
'In other words, it may not be the case that changing your habits changes your risk of breast cancer; it may be more complex than that.
The team speculated that this mismatch may have its own impact on cancer risk, but making that connection will require more extensive research.
"These intriguing results add to the growing body of evidence that there is some overlap between the genetics of when we'd prefer to sleep and our breast cancer risk, but more research is required to unravel the specifics of this relationship", he said.
Researchers also looked at results from nearly 229,000 women signed up to an worldwide genetic study carried out by the Breast Cancer Association Consortium.
They utilized a genetic method known as Mendelian randomization in which genetic variants associated with possible risk factors, such as sleep characteristics, were analyzed.
The researchers believe their findings have implications for policy-makers and employers.
Careem, one of the region's leading technology organisations, launched a breast cancer awareness campaign in partnership with the Qatar Cancer Society (QCS) last October.
"The authors do not show any biological mechanism by which sleep timing preference could influence breast cancer risk".
"Sleep is likely to be an important risk factor for breast cancer", she said. The World Health Organization already says disruption to people's body clocks because of shift work is probably linked to cancer risk. "Another limitation is that sleep timing preference (chronotype) is self-reported, and the investigation did not specifically recruit individuals with different sleep patterns, such as night-shift workers", Burgess wrote in the comments of the study. "I wouldn't support that women should get up earlier to reduce risk of breast cancer".
Experts not involved in the research welcomed the findings - although they cautioned that it was too early to change any behaviour until more research can be conducted.