A study out of Japan involving almost 24,000 women found that those who got less than 7 hours of sleep each night were at a higher risk for developing breast cancer.
Researchers split participants into categories according to their sleep duration and determined the estimated hazard ratio for developing breast cancer for each group based on how much sleep they got.
The results found that the hazard ratio for women who got 6 or fewer hours of sleep was 1.62 (the baseline hazard ratio for those who got 7 hours of sleep per night was 1.00).
Those who slept for 9 hours or more saw a reduced risk of developing breast cancer - that group's hazard ratio was 0.72.
So why the link between sleep duration and breast cancer?
It's thought that melatonin may have some part to play here - one theory suggests that the lower levels of melatonin typically seen in those who suffer from insomnia may be behind the increased risk.
It has been argued that melatonin may help prevent the development of breast cancer cells; so those with lower levels of the hormone may naturally be at a higher risk of developing the disease.
For more details, check out the source link below.
Source: British Journal of Cancer
Last updated: October 3, 2013